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The spectral sensitivities of the middle- and long-wavelength-sensitive cones derived from measurements in observers of known genotype
Abstract
The spectral sensitivities of middle- (M-) and long- (L-) wavelength-sensitive cones have been measured in dichromats of known genotype: M-cone sensitivities in nine protanopes, and L-cone sensitivities in 20 deuteranopes. We have used these dichromat cone spectral sensitivities, along with new luminous efficiency determinations, and existing spectral sensitivity and color matching data from normal trichromats, to derive estimates of the human M- and L-cone spectral sensitivities for 2 and 10 degrees dia. central targets, and an estimate of the photopic luminosity function [V(lambda)] for 2 degrees dia. targets, which we refer to as V(2)*(lambda). These new estimates are consistent with dichromatic and trichromatic spectral sensitivities and color matches.
... In 2006, the CIE adopted 2 and 10 LMS cone fundamentals that were based almost entirely on the work of Stockman, Sharpe and Fach 15 and Stockman & Sharpe. 16 They measured cone spectral sensitivities in dichromats (lacking either L-or M-cones), S-cone monochromats (lacking both L-and M-cones) and observers with normal color vision, all of known photopigment genotype, from which they defined the cone fundamentals as a linear combination of the 10 CMFs Stiles and Burch observers. 3 Their work also included estimates of the optical density spectra of the macular and lens pigments, the three photopigment spectral absorbance curves and the cone photopigment optical densities, all of which were incorporated in CIE 2006 2 and 10 standards. ...
... We analyzed the effects of individual differences on the color matches by applying the CIEPO06 model based on Stockman and Sharpe [15][16][17][18] and extended by Stockman and Rider. 19 This model allows us to easily generate cone spectral sensitivities with different macular and lens pigment optical densities, different cone photopigment spectral shifts and different photopigment optical densities. ...
... The CIEPO06 L-cone fundamental was not used for this analysis because it is an average of the L(ser180) and L(ala180) cone fundamentals in the ratio of 0.56:0.44 (see for details Ref. 16,19). Instead, we used the L(ser180) cone fundamental from that paper, the continuous formula for which is given in Table 4 of Stockman and Rider. 2 In this type of analysis, single rather than mixed photopigment spectra are required. ...
Measuring color matching differences between observers is an important means of investigating individual differences in human color vision. In this article, we introduce a new LED-based visual trichromator with which we have estimated color matching functions and cone spectral sensitivities in a group of five normal observers. The trichromator has side-by-side semi-circular matching fields that are illuminated by two spectrally tunable LED light sources, each comprised of 18 LEDs with center wavelengths ranging from 400 to 700 nm. We used Maxwell's method to derive a set color match. A fixed triplet of red-green-blue (RGB) primaries produced the white standard field of 120 cd/m 2 in one field. The other field, the mixture field, was illuminated by one of 11 different triplets of lights with various center wavelengths. Observers adjusted the intensities of the triplets in the mixture field to match the white standard field. All matches were made for field diameters of 2 and 10 of visual angle to allow comparisons with colorimetric standards and were repeated five times. Calibrations and tests showed that the trichromator and the measurements were stable and repeatable. Grassmann's laws predict that at the 11 color matches the excitations in the three cone types should be the same. Consequently, we can use those matches and a model of how cone spectral sensitivities vary between individuals to estimate the three underlying cor-neal cone spectral sensitivities for each observer (and thus how they vary from the standard (or mean) observer). We find good agreement with the CIE 2006 standards, but our observers show small but consistent differences.
... Cones have distinct spectra. The cyanolable S-cone opsin has sensitive peaks to wavelengths up to 420 nm; the M cones contain chlorolabe, with a peak sensitivity of 530 nm; and the L cones contain a red-sensitive opsin (erythrolable), with a maximum peak of 560 nm [32]. However, this radiation does not reach the retina without passing through the refractive media of the human eyes. ...
... Background evidence is divided regarding the effectiveness of blue light-blocking lenses. While some say that ophthalmic lenses can be a resource and have been shown to effectively attenuate blue light exposure, impacting circadian rhythm and photoreceptor function [40], others state they find no evidence to support the use of blue light-blocking lenses to improve visual performance, sleep quality, alleviate eye strain, or maintain macular health [32]. However, we can state that lenses have been shown to effectively attenuate the spectral emission of blue light, although this selective blocking of light may have consequences for visual function and color perception. ...
... Decreasing the intensity of blue light will provide the benefits of better sleep and protection against potential eye diseases, but more research is needed to investigate this potential health risk [32]. ...
The prevalence of digital devices in modern society has raised concerns about the potential negative effects of blue-light emissions on eye health and biological rhythms. Research into blue light emissions from digital devices and their potential impact on eye health emphasizes the importance of understanding and quantifying the extent and scope of blue light emissions produced by commonly used screens (smartphones, tablets, and computers). The goal of this study was to implement a set of methodologies to analyze this emission. A comparative study specifically evaluated three popular Apple devices: the iPhone 12 mini®, iPad Pro 12.9®, and the MacBook Pro®. The devices’ spectral power was measured using a spectroradiometer while displaying text and a game at different brightness levels. The laboratory measurements are compared to known solar irradiance, and all devices tested show blue wavelength peaks between 445 nm and 455 nm, with no expected immediate photobiological risk. We quantified the spectral emission from the three device categories and concluded that blue light levels should not significantly affect eye health. The measurements carried out indicated that the blue irradiance received by the human eye during one minute outdoors is greater than the blue light received by digital devices in approximately 24 h. This study also examines the effectiveness of blue-blocking lenses from well-known brands. The research highlights the importance of quantifying blue light emissions and understanding their potential impact on eye health, so appropriate measures can be developed to mitigate, if needed, adverse effects on ocular structures. A need to clarify the efficacy and usefulness of blue-blocking ophthalmic lenses still remains.
... Radiance spectra were converted 109 into L, M, and S cone excitations based on the Stockman and Sharpe 2 cone spectral sensitivities, lens, and macular pigment data. 108,105 Spectrally shifted absorption spectra were derived from a quadratic loess fit 121 to the normal L, M, and S absorption spectra on a scale of radiance versus log wavelength, with optimal loess bandwidth determined by cross-validation. 106 The normal L, M, and S pigments were assumed to have maximum sensitivities at approximately 559, 530, and 426 nm, respectively. ...
... 106 The normal L, M, and S pigments were assumed to have maximum sensitivities at approximately 559, 530, and 426 nm, respectively. 5, 105,122 In protanomaly, the normal and hybrid medium-to-long-wavelength cone pigments were assumed to have maximum sensitivities at approximately 530 and 536 nm, respectively, and in deuteranomaly, at 559 and 549 nm. 5 The sizes of the hybrid shifts were intended to illustrate their range, not necessarily their prevalence. Optical density was taken to be constant. ...
... In brief, let Lðu; v; lÞ be the reflected radiance, indexed by spatial coordinates u, v and wavelength l, and let S L ðlÞ; S M ðlÞ; S S ðlÞ be, respectively, the long-, medium-, and short-wavelength-sensitive cone spectral sensitivities, measured at the cornea, that is, incorporating preceptor absorption. 105 where integration is over the visible range. 109 How scene information was calculated from these cone excitations with normal, hybrid, or absent photopigments is described later. ...
Inherited color vision deficiency affects red-green discrimination in about one in twelve men from European populations. Its effects have been studied mainly in primitive foraging but also in detecting blushing and breaking camouflage. Yet there is no obvious relationship between these specific tasks and vision in the real world. The aim here was to quantify the impact of color vision deficiency by estimating computationally the information available to observers about colored surfaces in natural scenes. With representative independent sets of 50 and 100 hyperspectral images, estimated information was found to be only a little less in red-green color vision deficiency than in normal trichromacy. Colorimetric analyses revealed the importance of large lightness variations within scenes, small redness-greenness variations, and uneven frequencies of different colored surfaces. While red-green color vision deficiency poses challenges in some tasks, it has much less effect on gaining information from natural environments.
... Although the sensitivity spectra of human retinal cones is usually performed by invasive approaches such as ex-vivo retinal unit recordings 7 and psychophysical color matching 8 , the color perceptual response is usually studied noninvasively in humans using methods such as magnetoencephalography (MEG) 9 and functional-magneticresonance-imaging (fMRI) 10 . The research on human 11 and non-human 12 primates showed that visual stimuli often induce gamma-band rhythmic activity (neuronal gamma-band is 30-100 Hz, and induced gamma-bands is around 40 Hz for low-gamma and 80 Hz for high-gamma)in the early visual cortex which can be dependent on specific feature values in the presented visual stimuli such as contrast and color 9 . ...
... The prefrontal area (F7-F5-Fp1-FT7-Fp2-Fpz-FC5-AF7-AF3-AF8-F3-F1) are significant site (5000 permutations, cluster-forming threshold Z > 1.96, corrected significance threshold p < 0.05). Fig. 5D-left, we demonstrated the ITPC average in theta-band frequency (4)(5)(6)(7)(8). Notably, after 200 ms post-stimulus onset, all colors showed similar behavior. ...
The perception of color is a fundamental cognitive feature of our psychological experience, with an essential role in many aspects of human behavior. Several studies used magnetoencephalography, functional magnetic resonance imaging, and electroencephalography (EEG) approaches to investigate color perception. Their methods includes the event-related potential and spectral power activity of different color spaces, such as Derrington-Krauskopf-Lennie and red-green-blue (RGB), in addition to exploring the psychological and emotional effects of colors. However, we found insufficient studies in RGB space that considered combining all aspects of EEG signals. Thus, in the present study, focusing on RGB stimuli and using a data-driven approach, we investigated significant differences in the perception of colors. Our findings show that beta oscillation of green compared to red and blue colors occurs in early sensory periods with a latency shifting in the occipital region. Furthermore, in the occipital region, the theta power of the blue color decreases noticeably compared to the other colors. Concurrently, in the prefrontal area, we observed an increase in phase consistency in response to the green color, while the blue color showed a decrease. Therefore, our results can be used to interpret the brain activity mechanism of color perception in RGB color space and to choose suitable colors for more efficient performance in cognitive activities.
... The second-step classification results agreed for all 19 CN observers and five out of nine AT observers. The remaining four AT observers (CVD#7, 11,15,17) received inconsistent diagnoses from HRR and FM100; therefore for FInD classification, we assigned them to the CVD categories in which the members in their clusters fell, which necessarily agreed with one of their HRR or FM100 diagnoses, but not both. It is worth noting that for one cluster (CVD#12, 15,17), although one of the participants (CVD#12) received consistent HRR and FM100 diagnoses in the test session, the retest HRR diagnosis changed type, so that all three participants received confusing HRR and FM100 diagnoses when the retest session results were considered. ...
... The remaining four AT observers (CVD#7, 11,15,17) received inconsistent diagnoses from HRR and FM100; therefore for FInD classification, we assigned them to the CVD categories in which the members in their clusters fell, which necessarily agreed with one of their HRR or FM100 diagnoses, but not both. It is worth noting that for one cluster (CVD#12, 15,17), although one of the participants (CVD#12) received consistent HRR and FM100 diagnoses in the test session, the retest HRR diagnosis changed type, so that all three participants received confusing HRR and FM100 diagnoses when the retest session results were considered. This cluster is referred to as the unknown AT group. ...
Colour vision deficiencies (CVDs) indicate potential genetic variations and can be important biomarkers of acquired impairment in many neuro-ophthalmic diseases. However, CVDs are typically measured with tests which possess high sensitivity for detecting the presence of a CVD but do not quantify its type or severity. In this study, we introduce Foraging Interactive D-prime (FInD), a novel computer-based, generalisable, rapid, self-administered vision assessment tool and apply it to colour vision testing. This signal detection theory-based adaptive paradigm computed test stimulus intensity from d-prime analysis. Stimuli were chromatic Gaussian blobs in dynamic luminance noise, and participants clicked on cells that contained chromatic blobs (detection) or blob pairs of differing colours (discrimination). Sensitivity and repeatability of FInD colour tasks were compared against the Hardy-Rand-Rittler and the Farnsworth-Munsell 100 hue tests in 19 colour-normal and 18 inherited colour-atypical, age-matched observers. Rayleigh colour match was also completed. Detection and discrimination thresholds were higher for atypical than for typical observers, with selective threshold elevations corresponding to unique CVD types. Classifications of CVD type and severity via unsupervised machine learning confirmed functional subtypes. FInD tasks reliably detect inherited CVDs, and may serve as valuable tools in basic and clinical colour vision science.
... We produced multispectral images standardised and linearised against the 25% reflectance standard, and converted them to predator vision (Troscianko and Stevens 2015). Because of the experimental approach, the local predator community, and the lack of appropriate UV images, we used a human trichromatic vision model (Stockman and Sharpe 2000) to represent the sensory system of predators. ...
Camouflage represents an important component of self-protection when animals cannot easily evade predators and is often altered by behavioural responses to a predation threat. The cryptic plumage of many precocial chicks inspired early theoretical work on camouflage mechanisms, but so far, limited efforts have gone towards empirically testing the crypsis of chick plumage properties in their natural environment. We studied background matching and hiding behaviour in precocial snowy plovers Charadrius nivosus in Bahia de Ceuta, Northwest Mexico. This ground-nesting wader breeds in sparsely vegetated open habitats such as salt flats and sandy beaches. The open habitats provide a challenge for young chicks to evade predator detection. Examining background matching of wild chicks for luminance, pattern and colouration at their hiding spots, we found that chicks matched the luminance of their chosen spot better than at unchosen nearby spots. Pattern and colouration matching were age-related, with the plumage of older chicks matching their hiding spots better than those of recently hatched chicks. This suggests that with increasing mobility, chicks may be better able to find hiding places that optimise camouflage. Finally, we found that chicks were more likely to hide in soil cracks than expected by chance, suggesting that chicks chose these soil features in a barren landscape as preferred hideouts. We conclude that the cryptic plumage is an understudied but essential part of the anti-predator repertoire of precocial chicks. The plumage most likely works hand-in-hand with the anti-predator behaviours of chicks and their parents to increase survival chances of precocial young.
Significance statement
Many chicks rely on effective camouflage to evade predators and survive until fledging. We studied how plumage characteristics and behavioural choices enable snowy plover chicks to hide effectively from approaching predators in an open landscape. These chicks leave their nest scrapes shortly after hatching, relying on their cryptic plumage for several weeks to evade predator detection. We found that chicks chose hiding spots where their plumage had a higher match in luminance and, for older chicks, a higher match in pattern and colouration than at adjacent spots. When available, chicks chose to hide in small cracks that appeared in the soil from the evaporation of moisture. This study represents the first quantitative characterisation of cryptic chick plumage features in a natural population. Our results demonstrate that plumage and behavioural responses jointly contribute to the effective camouflage of small chicks.
... Further genetic analysis of these populations would be extremely useful in confirming or refuting a hybrid gene hypothesis. Also relevant is the fact that the genotyped dichromat observers who contributed data to produce the Stockman and Sharpe cone fundamentals (i.e., the CIEPO06 standard) were all male single-gene dichromats known to have either wildtype M opsin or L with serine at amino acid position 180 [32,33] meaning their Land M-cone spectral positions were located at the extremes of the general population. Thus, the CIEPO06 spectral sensitivities do not include polymorphic variants that might shift the M-cone photopigment to slightly longer wavelengths and the L-cone pigment to slightly shorter wavelengths. ...
Forty-six young adult observers with normal color vision (plus five from an earlier study) made a series of color matches using a new LED-based, multi-wavelength visual trichromator. Thirteen LED lights of different wavelengths were combined to produce 11 triplets of lights that observers were asked to match to a white reference light of 7500 K over visual angles of either 2° or 10°. Matches were initially made by asking observers to adjust the intensities of the three lights making up each triplet. As the experiment progressed, a more intuitive matching procedure was developed. By transforming the triplet of lights into CIELAB space, observers adjusted colors using lightness (L*), redness-greenness (a*), and blueness-yellowness (b*) to make the match with white. The new procedure proved easier for observers and reduced the inter- and intra-observer variability. Given that each of the 11 matches to the reference white for a given observer (obtained by either method) should produce identical L-, M- and S-cone excitations, we were able to use the matches to infer the individual cone spectral sensitivities for each observer and thus estimate the range of individual differences across our 51 observers. By applying a model of the CIEPO06 standard LMS observer, the photopigment, macular and lens optical densities and the L- and M-cone photopigment spectral shifts that best equated the three-cone excitations across the 11 matches were found for each observer. The individual differences were consistent with the CIEPO06 observer except for a 3 nm shift of the M-cone photopigment to longer wavelengths and a slightly denser 2-deg macular pigment density.
... Thus, the actual proportion of S-cones in the model mosaic was lower than 7%. The spectral quantum efficiency of the S-, M-, and L-cones were based on Stockman & Sharp [24,25]. We used a lens age of 32 years when computing the retinal image, and macular pigment optical density (MPOD) that varied across the mosaic with a peak of 0.35 at the fovea. ...
It has been known for more than 220 years that the image quality of the human eye is significantly degraded by chromatic aberrations. Recently, it was shown experimentally that correcting chromatic aberrations results in a 0.2- to 0.8-line improvement in visual acuity. Here we ask, is this expected? We developed tools that enable simulations of the optical impact of physiologically relevant amounts of chromatic aberration in real human eyes and combined these with tools that compute the visual acuity of an ideal observer. This allows us to characterize the theoretical impact of chromatic aberration correction on visual acuity. Results indicate a substantive improvement of 0.4- to 2-lines in ideal observer visual acuity with chromatic aberration correction. Ideal observer thresholds benefit significantly more from correction of longitudinal than correction of transverse chromatic aberration. Finally, improvements in ideal observer visual acuity are greater for subjects with less monochromatic aberration, such that subjects with better baseline optical quality benefit most from correction of chromatic aberrations.
... The convolution with the filter kernel, however, is not performed on the original images whose colors are defined by their u ,v ,L values (see the Stimulus section), but rather, in order to account for cone opponency, on images whose pixels represent the respective combination of different cone excitations. That is, the u ,v ,L images were first converted to LMS coordinates (based on Stockman & Sharpe, 2000) and then converted into maps whose pixel values represent either L-M (for stimuli of the RG color condition) or S-(L+M) (for stimuli that belong to the BY color condition; see step 1 in Figure 8). As in our previous study, the optimal size of the respective filter kernel is determined empirically when the model parameters are fitted with the experimental data. ...
The phenomenon of binocular luster can be evoked by simple dichoptic center-surround stimuli showing a luminance contrast difference between the eyes. Previous findings support the idea that this phenomenon is mediated by a low-level conflict mechanism that integrates the monocular signals from different types of contrast detector cells. Also, isoluminant stimuli with different chromatic contrasts between eyes can trigger sensations of luster. Here, we investigate whether the lustrous impression in such purely chromatic stimuli depends on interocular contrast differences and in particular on interocular contrast polarity pairings in a similar way as in the achromatic case. In our experiments, we measured the magnitude of the lustrous response using a series of isoluminant dichoptic center-ring-surround stimuli with varying ring width whose chromatic properties were varied along the red-green and blue-yellow cardinal directions. The trends in the data were very similar to those of our former study with achromatic stimuli, indicating similar mechanisms in both cases. The empirical luster data could also be predicted fairly well by a chromatic version of our interocular conflict model (with overall R2 values between 0.577 and 0.639), for which two different receptive field models were used, simulating the behavior of color-sensitive double-opponent cells in V1.
... Eventually, this committee agreed on the CIE 2006 2° and 10° colour matching functions and on a model for estimating how they change between 1° and 10° based on changes in the optical densities of the cone photopigments, and macular and lens pigments [19][20][21]. This became known as the physiological observer model (CIEPO06) [19], which is largely based on the research findings and proposals of Stockman and Sharpe [22]. Starting from the 10° colour matching functions of 47 Stiles-Burch observers [23], this model defines the fundamental observers for 2° and 10° and provides a convenient framework for calculating the average cone spectral sensitivities for any visual field size between 1° and 10° and for ages ranging from 20 to 80 years old. ...
... We decided to pick 8 bands in total, spanning the visible range. We used the 2 degrees LMS from Stockman and Sharpe [44,43], as presented in http://www.cvrl.org/. We also include the rod sensitivities, i.e. the scotopic luminosity function from CIE-1951 [5], data from the same website. ...
The variety of spectral imaging systems makes the portability
of imaging solutions and the generalization of research difficult.
We advocate for the creation of a standard representation space
for spectral imaging. We propose a space that allows connection
to colorimetric standards and to spectral reflectance factors,
while keeping a low and practical dimension. The performance
of one instance of this standard is evaluated through simulations.
Results demonstrate that this space may show reduced performance in accuracy than some native camera spaces, especially instances with a number of bands larger than the standardized dimension, but this limitation comes with benefit in size and standardization.
... Thus, responses evoked by differentially stimulating particular classes of cone (here, the L-cones more than M-cones) may not behave in the same way, including in terms of GABA modulation, as white stimuli that are presumed to stimulate all classes equally. As well as delivering lower retinal illuminance (the photopic strength of the red flashes and blue background were both around half the strength of the white flashes and background), the red flashes (621 nm) would be estimated, based on published spectral sensitivities (Stockman and Sharpe, 2000), to stimulate the L-cones around five times more strongly than the M-cones, with minimal S-cone stimulation. Another possible explanation is that red-on-blue flashes in the PhNR protocol triggered different ON and/or OFF inputs compared with the standard white flashes and hence the differential a-wave and b-wave responses driven by L-and M-cones (Kremers et al., 2021). ...
Alterations in γ-aminobutyric acid (GABA) have been implicated in sensory differences in individuals with autism spectrum disorder (ASD). Visual signals are initially processed in the retina, and in this study, we explored the hypotheses that the GABA-dependent retinal response to light is altered in individuals with ASD. Light-adapted electroretinograms were recorded from 61 adults (38 males and 23 females; n = 22 ASD) in response to three stimulus protocols: (1) the standard white flash, (2) the standard 30 Hz flickering protocol, and (3) the photopic negative response protocol. Participants were administered an oral dose of placebo, 15 or 30 mg of arbaclofen (STX209, GABA B agonist) in a randomized, double-blind, crossover order before the test. At baseline (placebo), the a-wave amplitudes in response to single white flashes were more prominent in ASD, relative to typically developed (TD) participants. Arbaclofen was associated with a decrease in the a-wave amplitude in ASD, but an increase in TD, eliminating the group difference observed at baseline. The extent of this arbaclofen-elicited shift significantly correlated with the arbaclofen-elicited shift in cortical responses to auditory stimuli as measured by using an electroencephalogram in our prior study and with broader autistic traits measured with the autism quotient across the whole cohort. Hence, GABA-dependent differences in retinal light processing in ASD appear to be an accessible component of a wider autistic difference in the central processing of sensory information, which may be upstream of more complex autistic phenotypes.
... However, in practice, the luminosity function is only accurate for the test condition under which it is determined [10]. The most commonly used luminosity function was originally recommended by the CIE in 1924 and was later modified by D.B. Judd in 1951 and J.J. Vos in 1978 [11]. Most recently, Sharpe et al. revisited this topic and obtained an improved relationship for standard daylight conditions [10]. ...
The perceived value of paper products depends not only upon their performance but also upon their visual appeal. The optical properties of paper, including whiteness, brightness, opacity, and gloss, affect its visual perception and appeal. From a practical point of view, it is important to quantify these optical properties by means of reliable and repeatable measurement methods, and furthermore, to relate these measured values to the structure of paper and characteristics of its constituents. This would allow papermakers to design new products with improved quality and reduced cost. In recent years, significant progress has been made in terms of the fundamental understanding of light-paper interaction and its effect on paper’s appearance. The introduction of digital imaging technology has led to the emergence of a new category of optical testing methods and has provided fresh insights into the relationship between paper’s structure and its optical properties. These developments were complemented by advances in the theoretical treatment of light propagation in paper. In particular, wave scattering theories in random media are finding increasing applicability in gaining a better understanding of the optical properties of paper. In this document, a review of these advancements is presented.
... Note the similarity of the M and L cones, where minor individual differences can result in an unresolvable overlap, causing observers to have a reduced ability to differentiate between lights in the red-green region. This is plotted based on Stockman and Sharpe[23]. ...
Over 300 million people who live with color vision deficiency (CVD) have a decreased ability to distinguish between colors, limiting their ability to interact with websites and software packages. User-interface designers have taken various approaches to tackle the issue, with most offering a high-contrast mode. The Web Content Accessibility Guidelines (WCAG) outline some best practices for maintaining accessibility that have been adopted and recommended by several governments; however, it is currently uncertain how this impacts perceived user functionality and if this could result in a reduced aesthetic look. In the absence of subjective data, we aim to investigate how a CVD observer might rate the functionality and aesthetics of existing UIs. However, the design of a comparative study of CVD vs. non-CVD populations is inherently hard; therefore, we build on the successful field of physiologically based CVD models and propose a novel simulation-based experimental protocol, where non-CVD observers rate the relative aesthetics and functionality of screenshots of 20 popular websites as seen in full color vs. with simulated CVD. Our results show that relative aesthetics and functionality correlate positively and that an operating-system-wide high-contrast mode can reduce both aesthetics and functionality. While our results are only valid in the context of simulated CVD screenshots, the approach has the benefit of being easily deployable, and can help to spot a number of common pitfalls in production. Finally, we propose a AAA–A classification of the interfaces we analyzed.
... The method of silent substitution has been used in the field of colorimetry for decades (Estévez and Spekreijse, 1982) and it provides mechanistic insights into selective photoreceptor contributions. This is possible because photoreceptor output is univariant, depending only on the amount of photons absorbed by the photopigments in each effectively color blind photoreceptor (Rushton, 1972;Spitschan and Woelders, 2018;Stockman and Sharpe, 2000). Therefore, lights with different spectra can lead to the same photoreceptor excitation. ...
The pupil modulates the amount of light that reaches the retina. Not only luminance but also the spectral distribution defines the pupil size. Previous research has identified steady-state pupil size and melatonin attenuation to be predominantly driven by melanopsin, which is expressed by a unique subgroup of intrinsically photosensitive retinal ganglion cells (ipRGCs) that are sensitive to short-wavelength light (~480 nm). Here, we aimed to selectively target the melanopsin system during the evening, while measuring steady-state pupil size and melatonin concentrations under commonly experienced evening light levels (<90 lx). Therefore, we used a five-primary display prototype to generate light conditions that were matched in terms of L-, M-, and S-cone-opic irradiances, but with high and low melanopic irradiances (~3-fold difference). Seventy-two healthy, male participants completed a 2-week study protocol. The volunteers were assigned to one of the four groups that differed in luminance levels (27-285 cd/m ² ). Within the four groups, each volunteer was exposed to a low melanopic (LM) and a high melanopic (HM) condition. The two 17-h study protocols comprised 3.5 h of light exposure starting 4 h before habitual bedtime. Median pupil size was significantly smaller during HM than LM in all four light intensity groups. In addition, we observed a significant correlation between melanopic weighted corneal illuminance (melanopic equivalent daylight illuminance [mEDI]) and pupil size, such that higher mEDI values were associated with smaller pupil size. Using pupil size to estimate retinal irradiance showed a qualitatively similar goodness of fit as mEDI for predicting melatonin suppression. Based on our results here, it remains appropriate to use melanopic irradiance measured at eye level when comparing light-dependent effects on evening melatonin concentrations in healthy young people at rather low light levels.
... Images by James Tumulty, used with permission and reproduced from Tumulty et al. (2023). catch values using the vismodel function in pavo using human spectral sensitivities (Stockman & Sharpe, 2000). We calculated luminance (achromatic) receptor stimulation by averaging the summed response for the medium-and long-wavelength photoreceptors (Eisner & MacLeod, 1980;Guth et al., 1968). ...
Colour pattern variation provides biological information in fields ranging from disease ecology to speciation dynamics. Comparing colour pattern geometries across images requires colour segmentation, where pixels in an image are assigned to one of a set of colour classes shared by all images. Manual methods for colour segmentation are slow and subjective, while automated methods can struggle with high technical variation in aggregate image sets. We present recolorize, an R package toolbox for human‐subjective colour segmentation with functions for batch‐processing low‐variation image sets and additional tools for handling images from diverse (high‐variation) sources. The package also includes export options for a variety of formats and colour analysis packages. This paper illustrates recolorize for three example datasets, including high variation, batch processing and combining with reflectance spectra, and demonstrates the downstream use of methods that rely on this output.
... Then, the radiance spectrum needs to be converted to 'tri-stimulus' values to simulate their apparent colours to the 'average' human eye (see Appendix A ), multiplying by the colour-matching functions of the XYZ colour space of the Commission Internationale de l' É clairage (CIE) and integrating, and then transforming the resulting XYZ colours to the standard RGB (sRGB) colour space (e.g. Stockman & Sharpe 2000 ;Stockman 2019 ). This process reduces the spectrum at each pixel to its threecolour sRGB representation. ...
We present a quantitative analysis of the seasonal record of Uranus’s disc-averaged colour and photometric magnitude in Strömgren b and y filters (centred at 467 and 551 nm, respectively), recorded at the Lowell Observatory from 1950 to 2016, and supplemented with HST/WFC3 observations from 2016 to 2022. We find that the seasonal variations of magnitude can be explained by the lower abundance of methane at polar latitudes combined with a time-dependent increase of the reflectivity of the aerosol particles in layer near the methane condensation level at 1 – 2 bar. This increase in reflectivity is consistent with the addition of conservatively scattering particles to this layer, for which the modelled background haze particles are strongly absorbing at both blue and red wavelengths. We suggest that this additional component may come from a higher proportion of methane ice particles. We suggest that the increase in reflectivity of Uranus in both filters between the equinoxes in 1966 and 2007, noted by previous authors, might be related to Uranus’s distance from the Sun and the production rate of dark photochemical haze products. Finally, we find that although the visible colour of Uranus is less blue than Neptune, due to the increased aerosol thickness on Uranus, and this difference is greatest at Uranus’s solstices, it is much less significant than is commonly believed due to a long-standing misperception of Neptune’s ‘true’ colour. We describe how filter-imaging observations, such as those from Voyager-2/ISS and HST/WFC3, should be processed to yield accurate true colour representations.
... The human retinal imaging results presented in Section 4.C utilized the 680 nm and 840 nm channels. Although here the 543 nm channel was used for ease of alignment and system validation, it was configured for use in future imaging experiments that require stimulation of both M and L cones, which have approximately equal sensitivity to 543 nm light [28,29]. Each of these three channels is equipped with a photomultiplier tube (PMT) for recording the backscattered light from the retina and accurately localizing the stimulus position on the retina, which is essential for studying fixational eye movements and visual perception in AOSLO psychophysics experiments. ...
In prior art, advances in adaptive optics scanning laser ophthalmoscope (AOSLO) technology have enabled cones in the human fovea to be resolved in healthy eyes with normal vision and low to moderate refractive errors, providing new insight into human foveal anatomy, visual perception, and retinal degenerative diseases. These high-resolution ophthalmoscopes require careful alignment of each optical subsystem to ensure diffraction-limited imaging performance, which is necessary for resolving the smallest foveal cones. This paper presents a systematic and rigorous methodology for building, aligning, calibrating, and testing an AOSLO designed for imaging the cone mosaic of the central fovea in humans with cellular resolution. This methodology uses a two-stage alignment procedure and thorough system testing to achieve diffraction-limited performance. Results from retinal imaging of healthy human subjects under 30 years of age with refractive errors of less than 3.5 diopters using either 680 nm or 840 nm light show that the system can resolve cones at the very center of the fovea, the region where the cones are smallest and most densely packed.
... Radiance images were converted to estimated L, M, and S cone excitations at each point according to the CIE 2°cone fundamentals proposed by Stockman & Sharpe [45]. All colorimetric conversions, including the calibration of the monitor display, were implemented using the CIE 2°colour matching functions [43], which are also linear combinations of the Stockman & royalsocietypublishing.org/journal/rspb Proc. ...
The colours of surfaces in a scene may not appear constant with a change in the colour of the illumination. Yet even when colour constancy fails, human observers can usually discriminate changes in lighting from changes in surface reflecting properties. This operational ability has been attributed to the constancy of perceived colour relations between surfaces under illuminant changes, in turn based on approximately invariant spatial ratios of cone photoreceptor excitations. Natural deviations in these ratios may, however, lead to illuminant changes being misidentified. The aim of this work was to test whether such misidentifications occur with natural scenes and whether they are due to failures in relational colour constancy. Pairs of scene images from hyperspectral data were presented side-by-side on a computer-controlled display. On one side, the scene underwent illuminant changes and on the other side, it underwent the same changes but with images corrected for any residual deviations in spatial ratios. Observers systematically misidentified the corrected images as being due to illuminant changes. The frequency of errors increased with the size of the deviations, which were closely correlated with the estimated failures in relational colour constancy.
... For a LED lamp resembling L41 [9], the main uncertainty component would then come from the relative spectrum of the lamp influencing the spectral mismatch correction factor, where the relative spectral responsivity of the PQED would be known within a relative uncertainty of 0.01% or better. Such a PQED photometer without a physical filter would allow all types of photometric weighting to be taken into account numerically, for example scotopic, mesopic [96][97][98] or any new photometric weighting function based on cone fundamentals [99]. ...
Photometry contributes to our understanding how the world is perceived by the human visual system, where a specific example is an early study of photographic plates. Nowadays photometry has an important role in measurement of lighting, particularly in the transition from incandescent lighting to LED lighting. In the context of sustainability and energy efficiency, updated photometric methods are needed that address the spectral, colour, geometrical, and temporal characteristics of LED light sources. Highlights of the recent advances in these measurement methods are reviewed. Furthermore, challenges and achievements are described in the measurement of optical power, particularly related to the definition of the photometric SI base unit, the candela. These achievements are based on progress in the development of underpinning optical measurement standards, with a focus on technologies like the electrical substitution radiometer and the predictable quantum efficient detector. As a conclusion, the importance of ongoing research and development in photometry is emphasized considering its crucial role in supporting the advances of LED lighting technology and sustainable development goals of lighting industry.
... Let the C i , i ∈ {1, . . . , 51} be the CMFs of the Stiles and Burch experiments [29] and L t be the Stockman and Sharpe (2000) 10-deg cone fundamentals [34] (indicated as 10-LMS2000). The resulting dataset of individual observers represents a fundamental element of the present paper and is constituted by the cone fundamentals L i , i ∈ {1, . . . ...
Observer metamerism (OM) is the name given to the variability between the color matches that individual observers consider accurate. The standard color imaging approach, which uses color-matching functions of a single representative observer, does not accurately represent every individual observer’s perceptual properties. This paper investigates OM in color displays and proposes a quantitative assessment of the OM distribution across the chromaticity diagram. An OM metric is calculated from a database of individual LMS cone fundamentals and the spectral power distributions of the display’s primaries. Additionally, a visualization method is suggested to map the distribution of OM across the display’s color gamut. Through numerical assessment of OM using two distinct publicly available sets of individual observers’ functions, the influence of the selected dataset on the intensity and distribution of OM has been underscored. The case study of digital cinema has been investigated, specifically the transition from xenon-arc to laser projectors. The resulting heatmaps represent the “topography” of OM for both types of projectors. The paper also presents color difference values, showing that achromatic highlights could be particularly prone to disagreements between observers in laser-based cinema theaters. Overall, this study provides valuable resources for display manufacturers and researchers, offering insights into observer metamerism and facilitating the development of improved display technologies.
... The cone-contrast coordinates are functions of the Cone Fundamentals (Stockman and Sharpe, 2000) ...
In conceptual spaces, the distance between concepts is represented by a metric that cannot usually be expressed as a function of a few, salient physical properties of the represented items. For example, the space of colours can be endowed with a metric capturing the degree to which two chromatic stimuli are perceived as different. But as many optical illusions have shown, the colour with which a stimulus is perceived depends, among other contextual factors, on the chromaticity of its surround, an effect called "chromatic induction". The surround pushes the colour of the stimulus away from its own chromaticity, increasing the salience of the boundary. Previous studies have described how the magnitude of the push depends on the chromaticity of both the stimulus and the surround, concluding that the space of colours contains anisotropies and inhomogeneities. The importance of contextuality has cast doubt on the practical or predictive utility of perceptual metrics, beyond a mathematical curiosity. Here we provide evidence that the metric structure of the space of colours is indeed useful and has predictive power. By using a notion of distance between colours emerging from a subjective metric, we show that the anisotropies and inhomogeneities reported in previous studies can be eliminated. The resulting symmetry allows us to derive a universal curve for the average chromatic induction that contains no fitting parameters and is confirmed by experimental data. The theory also predicts the magnitude of chromatic induction for every possible combination of stimulus and surround demonstrating that, at least in the case of colours, the metric captures the symmetries of perception, and augments the predictive power of theories.
... Indeed, many trichromatic and tetrachromatic animals are unusually good at discriminating in the yellow-orange-red range-compared to other wavelength ranges-due in part to the placement of the medium and long wavelength-sensitive cones (Peiponen, 1992;Stockman & Sharpe, 2000). Birds vary in their wavelength discrimination abilities, but it is common to observe peak sensitivities in the orange-red (560 nm for green-backed firecrown, Sephanoides sephaniodes (Herrera et al., 2008); 555 and 585 nm for black-chinned hummingbirds, Archilochus alexandri (Goldsmith et al., 1981); 460, 540, and 600 nm for pigeon, Columba livia (Emmerton & Delhis, 1980); 416, 489 and 557 nm for budgerigar, Melopsittacus undulates (Goldsmith & Butler, 2003). ...
Carotenoid pigments are the basis for much red, orange, and yellow coloration in nature and central to visual signaling. However, as pigment concentration increases, carotenoid signals not only darken and become more saturated but they also redshift; for example, orange pigments can look red at higher concentration. This occurs because light experiences exponential attenuation, and carotenoid-based signals have spectrally asymmetric reflectance in the visible range. Adding pigment disproportionately affects the high-absorbance regions of the reflectance spectra, which redshifts the perceived hue. This carotenoid redshift is substantial and perceivable by animal observers. In addition, beyond pigment concentration, anything that increases the path length of light through pigment causes this redshift (including optical nano- and microstructures). For example, male Ramphocelus tanagers appear redder than females, despite the same population and concentration of carotenoids, due to microstructures that enhance light-pigment interaction. This mechanism of carotenoid redshift has sensory and evolutionary consequences for honest signaling in that structures that redshift carotenoid ornaments may decrease signal honesty. More generally, nearly all colorful signals vary in hue, saturation, and brightness as light-pigment interactions change, due to spectrally asymmetrical reflectance within the visible range of the relevant species. Therefore, the three attributes of color need to be considered together in studies of honest visual signaling.
... The LMS color space, also known as the cone-opponent color space, is a color model based on the responses of the three types of cones in the human visual system: the long-wavelength (L)(red) cones, the medium-wavelength (M)(green) cones, and the short-wavelength (S)(blue) cones. These cones are responsible for detecting different ranges of light wavelengths 13 . It is widely used in color vision research and provides a valuable tool for understanding color perception and visual processing, since it can be used to analyse and manipulate color stimuli based on the speci c responses along given chromatic axes corresponding to speci c pathways [14][15][16][17] . ...
Color perception entails competing temporal context mechanisms such as adaptation versus memory persistence ¹ . Perceptual dynamics in color cone pathways can be studied using the phenomenon of hysteresis, well-known in the framework of physical dynamical systems. It postulates analogous mechanisms: a) visual persistence defining positive hysteresis b) adaptation or habituation (negative hysteresis). Adaptation causes early perceptual switches to competing states. We investigated competition between these mechanisms in human color cone pathways. Color adaptation occurs within early visual pathways up to V4, involved in local scene analysis, but it is unknown if they underlie global perceptual binding of visual elements ² . We tested if the neural locus of perceptual binding occurs at visual and memory stages beyond the locus of color adaptation, using a dynamic color matching task in cone contrast space, along Blue-Yellow (S-(L + M) and Green-Red processing channels (L-M). Simple vs Compound stimuli required or not holistic perceptual binding, under visual or memory-guided conditions. Adaptation (negative hysteresis) dominated for the former condition, was stored in memory, but vanished when binding was required either in vision or memory. In sum, cone pathway adaptation mechanisms dominate in early vision, while perceptual binding occurs at a second stage as predicted by the feature integration theory.
... One uncertainty in a transfer of measurements from Z SD to Z CD is that Z SD is interpreted by human eyes, whereas Z CD is measured using digital quantum sensors. The human trichromatic color vision has a higher spectral sensitivity in the mid-PAR-spectra (Soffer & Lynch 1999;Stockman & Sharpe 2000). Compared to the human color vision, a quantum sensor instrument strives to have a relatively flat sensitivity curve throughout the whole PAR-spectrum (LI-COR 1990). ...
Light penetration plays a vital role in lakes and drinking water reservoirs, influencing fundamental processes such as primary production and thermal budgets. The Secchi depth (ZSD) and the compensation depth (ZCD) are commonly used measurements in this context. ZSD is determined through visual inspection using a Secchi disc, while ZCD represents the depth at which photosynthetic activity balances respiration and can be measured using a quantum irradiance sensor. Through in situ water-core samples from 23 lakes within a lake district in Southeastern Norway, we observed that DNOM exerts a diverse influence on these light irradiance measurements. If DNOM concentrations are reduced to half or a quarter of the current concentration, similar to what was measured during the 1980s, the median ZCD:ZSD ratios are estimated to have decreased by approximately 30 and 60% since then, respectively. Conversely, a plausible future climate-driven doubling or quadrupling of the present DNOM concentrations are estimated to further decrease the median ZCD:ZSD ratios in the lake district with approximately 10 and 25%, respectively. From this, the ZCD:ZSD ratios seem to have experienced a considerable long-term decline attributed to both climate change and the recovery from acid rain, and a further climate-driven decrease is expected.
HIGHLIGHTS
A long-term DNOM decline has had a diverse impact on two classical lake irradiance measurements – Secchi depth (ZSD) and compensation depth (ZCD) measurements.;
Irradiance measurements are affected by parameters scattering and absorbing light.;
ZCD is relatively more affected by DNOM.;
ZSD is relatively more affected by turbidity.;
ZCD:ZSD ratios have had a long-term decrease within a lake district in Norway.;
... (B) Cone isolation was achieved utilizing differences in spectral sensitivities. 85 In the S-cone-isolation condition, the subject viewed a blue letter E against a bright yellow background. In the L/M-coneisolation condition, the subject viewed a yellow letter E against a black background. ...
Purpose:
To measure photoreceptor packing density and S-cone spatial resolution as a function of retinal eccentricity in patients with enhanced S-cone syndrome (ESCS) and to discuss the possible mechanisms supporting their supernormal S-cone acuity.
Methods:
We used an adaptive optics scanning laser ophthalmoscope (AOSLO) to characterize photoreceptor packing. A custom non-AO display channel was used to measure L/M- and S-cone-mediated visual acuity during AOSLO imaging. Acuity measurements were obtained using a four-alternative, forced-choice, tumbling E paradigm along the temporal meridian between the fovea and 4° eccentricity in five of six patients and in seven control subjects. L/M acuity was tested by presenting long-pass-filtered optotypes on a black background, excluding wavelengths to which S-cones are sensitive. S-cone isolation was achieved using a two-color, blue-on-yellow chromatic adaptation method that was validated on three control subjects.
Results:
Inter-cone spacing measurements revealed a near-uniform cone density profile (ranging from 0.9-1.5 arcmin spacing) throughout the macula in ESCS. For comparison, normal cone density decreases by a factor of 14 from the fovea to 6°. Cone spacing of ESCS subjects was higher than normal in the fovea and subnormal beyond 2°. Compared to the control subjects (n = 7), S-cone-mediated acuities in patients with ESCS were normal near the fovea and became increasingly supernormal with retinal eccentricity. Beyond 2°, S-cone acuities were superior to L/M-cone-mediated acuity in the ESCS cohort, a reversal of the trend observed in normal retinas.
Conclusions:
Higher than normal parafoveal cone densities (presumably dominated by S-cones) confer better than normal S-cone-mediated acuity in ESCS subjects.
The increasing demand for white light‐emitting diode (WLED) has prompted the development of phosphors, in which Ce ³⁺ ‐activated garnet has been representative and widely investigated. The optimization and improvement of performance have long been a focus in the phosphor area. However, the trade‐off of phosphor performance always exists and is difficult to satisfy simultaneously, thereby necessitating a better understanding of the design principles that tune spectra performance comprehensively. Herein, the defect‐induced spectral tuning mechanism in a Ce‐doped garnet solid‐solution phosphor Ca 1.5‐ x Y 1.5+ x Al 3.5+ x Si 1.5‐ x O 12 :Ce ³⁺ (CYAS:Ce ³⁺ ) is promoted. The enhancement of luminescence intensity and thermal stability together with red‐shift of emission can be achieved by chemical unit co‐substitution of [Y ³⁺ ‐Al ³⁺ ] for [Ca ²⁺ ‐Si ⁴⁺ ], which originated from the increasing anti‐site vacancy. The related mechanism is fully elucidated by combining structural and spectral analysis with density functional theory (DFT) calculations. This study provides a subtle control for the performance‐tuning of phosphors, which can deepen the understanding of the design principle inside‐out and the subsequent development and exploration of novel optoelectronic functional materials.
The optical properties available for an object are most often fragmented and insufficient for photorealistic rendering of the object. We propose a procedure for digitizing a translucent object with sufficient information for predictive rendering of its appearance. Based on object material descriptions, we compute optical properties and validate or adjust this object appearance model based on comparison of simulation with spectrophotometric measurements of the bidirectional scattering-surface reflectance distribution function (BSSRDF). To ease this type of comparison, we provide an efficient simulation tool that computes the BSSRDF for a particular light-view configuration. Even with just a few configurations, the localized lighting in BSSRDF measurements is useful for assessing the appropriateness of computed or otherwise acquired optical properties. To validate an object appearance model in a more common lighting environment, we render the appearance of the obtained digital twin and assess the photorealism of our renderings through pixel-by-pixel comparison with photographs of the physical object.
Traditional fluorescent anti-counterfeiting materials usually exhibit fixed-wavelength excitation patterns and monochromatic luminescence, which are extremely easy to be counterfeited and have low security. Therefore, there is an urgent need to develop multi-mode fluorescent materials with enhanced security to address this issue. Here, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ core-shell structured phosphors were prepared via a sol-gel method. Coating SrAl2O4:Eu,Dy with Y2O3:Eu3+ red phosphor did not significantly change the crystal structure of SrAl2O4. Under UV excitation at 254 nm, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ exhibited red emission at 613 nm (5D0→7F2 transition of Eu3+), and a strong green afterglow was observed after removing the UV irradiation. However, blue-green emission at 496 nm was observed under UV excitation at 365 nm, followed by green afterglow upon removal of the light source. Varying the content of the Y2O3:Eu3+ shell yielded different emissions and afterglows. The prepared samples are sensitive to the excitation wavelength and duration and have multimodal luminescence properties, which can be used for anti-counterfeiting patterns. The outcomes in this work indicate that the phosphor is a promising fluorescent material for anti-counterfeiting.
Human photoreceptors consist of cones, rods, and melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). First studied in circadian regulation and pupillary control, ipRGCs project to a variety of brain centers suggesting a broader involvement beyond non-visual functions. IpRGC responses are stable, long-lasting, and with a particular codification of photoreceptor signals. In comparison with the transient and adaptive nature of cone and rod signals, ipRGCs' signaling might provide an ecological advantage to different attributes of color vision. Previous studies have indicated melanopsin's influence on visual responses yet its contribution to color perception in humans remains debated. We summarized evidence and hypotheses (from physiology, psychophysics, and natural image statistics) about direct and indirect involvement of ipRGCs in human color vision, by first briefly assessing the current knowledge about the role of melanopsin and ipRGCs in vision and codification of spectral signals. We then approached the question about melanopsin activation eliciting a color percept, discussing studies using the silent substitution method. Finally, we explore various avenues through which ipRGCs might impact color perception indirectly, such as through involvement in peripheral color matching, post-receptoral pathways, color constancy, long-term chromatic adaptation, and chromatic induction. While there is consensus about the role of ipRGCs in brightness perception, confirming its direct contribution to human color perception requires further investigation. We proposed potential approaches for future research, emphasizing the need for empirical validation and methodological thoroughness to elucidate the exact role of ipRGCs in human color vision.
Color constancy denotes the ability to assign a particular and stable color percept to an object, irrespective of its surroundings and illumination. The light reaching the eye confounds illumination and spectral reflectance of the object, making the recovery of constant object color an ill-posed problem. How good the visual system is at accomplishing this task is still a matter of heated debate, despite more than a 100 years of research. Depending on the laboratory task and the specific cues available to observers, color constancy was found to be at levels ranging between 15% and 80%, which seems incompatible with the relatively stable color appearance of objects around us and the consistent usage of color names in real life. Here, we show close-to-perfect color constancy using real objects in a natural task and natural environmental conditions, chosen to mimic the role of color constancy in everyday life. Participants had to identify the color of a (non-present) item familiar to them in an office room under five different experimental illuminations. They mostly selected the same colored Munsell chip as their match to the absent object, even though the light reaching the eye in each case differed substantially. Our results demonstrate that color constancy under ideal conditions in the real world can indeed be exceptionally good. We found it to be as good as visual memory permits and not generally compromised by sensory uncertainty.
Objectives
Investigate the visibility of new and old red, white and pink cricket balls under lighting and background conditions experienced during a day–night cricket match.
Design
We modelled the luminance contrast signals available for a typical observer for a ball against backgrounds in a professional cricket ground, at different times of day.
Methods
Spectral reflectance (light reflected as a function of wavelength) was derived from laboratory measurements of new and old red, white and pink balls. We also gathered spectral measurements from backgrounds (pitch, grass, sightscreens, crowd, sky) and spectral illuminance during a day–night match (natural afternoon light, through dusk to night under floodlights) from Lord's Cricket Ground (London, UK). The luminance contrast of the ball relative to the background was calculated for each combination of ball, time of day, and background surface.
Results
Old red and old pink balls may offer little or no contrast against the grass, pitch and crowd. New pink balls can also be of low contrast against the crowd at dusk, as can pink and white balls (of any age) against the sky at dusk.
Conclusions
Reports of difficulties with visibility of the pink ball are supported by our data. However, our modelling also shows that difficulties with visibility may also be expected under certain circumstances for red and white balls. The variable conditions in a cricket ground and the changing colour of an ageing ball make maintaining good visibility of the ball a challenge when playing day–night matches.
Keywords
SportVisionColourContrastDaylight
Practical implications
• Using measurements of the playing surfaces and light from a professional cricket ground, we modelled the visibility of the pink, red and white cricket balls.
• Player reports of difficulties seeing the pink ball are generally supported by our data.
•
The pink ball, introduced for use during dusk and night play may actually be more problematic against the pitch and sky.
• As balls wear during play their visibility can change substantially as the colour is dulled for red and pink balls, or the white surface is dirtied, so decisions about the choice of ball must take the effects of ball age into account.
• There is no single ball colour which is clearly suitable for all conditions to maximise visibility.
Two ideas, proposed by Thomas Young and James Clerk Maxwell, form the foundations of color science: (1) Three types of retinal receptors encode light under daytime conditions, and (2) color matching experiments establish the critical spectral properties of this encoding. Experimental quantification of these ideas are used in international color standards. But, for many years the field did not reach consensus on the spectral properties of the biological substrate of color matching: the sensitivity of the in situ cones (cone fundamentals). By combining auxiliary data (thresholds, inert pigment analyses), complex calculations, and color matching from genetically analyzed dichromats, the human cone fundamentals have now been standardized.
Here we describe a new computational method to estimate the cone fundamentals using only color matching from dichromatic observers. We show that it is not necessary to include data from trichromatic observers in the analysis or to know the primary lights used in the matching experiments. Remarkably, it is even possible to estimate the fundamentals by combining data from experiments using different, unknown primaries. We then suggest how the new method may be applied to color management in modern image systems.
The spectral shape, irradiance, direction, and diffuseness of daylight vary regularly throughout the day. The variations in illumination and their effect on the light reflected from objects may in turn provide visual information as to the time of day. We suggest that artists’ color choices for paintings of outdoor scenes might convey this information and that therefore the time of day might be decoded from the colors of paintings. Here we investigate whether human viewers’ estimates of the depicted time of day in paintings correlate with their image statistics, specifically chromaticity and luminance variations. We tested time-of-day perception in 17th- to 20th-century Western European paintings via two online rating experiments. In Experiment 1, viewers’ ratings from seven time choices varied significantly and largely consistently across paintings but with some ambiguity between morning and evening depictions. Analysis of the relationship between image statistics and ratings revealed correlations with the perceived time of day: higher “morningness” ratings associated with higher brightness, contrast, and saturation and darker yellow/brighter blue hues; “eveningness” with lower brightness, contrast, and saturation and darker blue/brighter yellow hues. Multiple linear regressions of extracted principal components yielded a predictive model that explained 76% of the variance in time-of-day perception. In Experiment 2, viewers rated paintings as morning or evening only; rating distributions differed significantly across paintings, and image statistics predicted people's perceptions. These results suggest that artists used different color palettes and patterns to depict different times of day, and the human visual system holds consistent assumptions about the variation of natural light depicted in paintings.
Unlike the exhaustive determination of cell types in the retina, key populations in the lateral geniculate nucleus of the thalamus (LGN) may have been missed. Here, we have begun to characterize the full range of extracellular neuronal responses in the LGN of awake monkeys using multi-electrodes during the presentation of colored noise visual stimuli to identify any previously overlooked signals. Extracellular spike waveforms of single units were classified into seven distinct classes, revealing previously unrecognized diversity: four negative-dominant classes that were narrow or broad, one triphasic class, and two positive-dominant classes. Based on their mapped receptive field (RF), these units were further categorized into either magnocellular ( M ), parvocellular ( P ), koniocellular ( K ), or non-RF ( N ). We found correlations between spike shape and mapped RF and response characteristics, with negative and narrow spiking waveform units predominantly associated with P and N RFs, and positive waveforms mostly linked to M RFs. Responses from positive waveforms exhibited shorter latencies, larger RF sizes, and were associated with larger eccentricities in the visual field than the other waveform classes. Additionally, N cells, those without an estimated RF, were consistently responsive to the visually presented mapping stimulus at a lower and more sustained rate than units with an RF. These findings suggest that the LGN cell population may be more diverse than previously believed.
Significance statement
This study uncovers evidence for an intricate diversity of neuronal responses within the lateral geniculate nucleus (LGN), challenging conventional classifications and revealing previously overlooked populations. By characterizing extracellular spike waveforms and revising receptive field classifications, we provide novel insights into LGN function. Our findings have significant implications for understanding early visual processing mechanisms and interpreting extracellular signals in neural circuits. Furthermore, we identify non-receptive field units, prompting exploration into their functional roles and broader implications for visual and non-visual computations. This study not only advances our understanding of LGN organization but also highlights the importance of considering recording biases in electrophysiological studies. Overall, our work opens new avenues for interdisciplinary research and contributes to advancing our knowledge of neural dynamics in the visual system.
The 2-photon effect in vision occurs when two photons of the same wavelength are absorbed by cone photopigment in the retina and create a visual sensation matching the appearance of light close to half their wavelength. This effect is especially salient for infrared light, where humans are mostly insensitive to 1-photon isomerizations and thus any perception is dominated by 2-photon isomerizations. This phenomenon can be made more readily visible using short-pulsed lasers, which increase the likelihood of 2-photon excitation by making photon arrivals at the retina more concentrated in time. Adaptive optics provides another avenue for enhancing the 2-photon effect by focusing light more tightly at the retina, thereby increasing the spatial concentration of incident photons. This article makes three contributions. First, we demonstrate through color-matching experiments that an adaptive optics correction can provide a 25-fold increase in the luminance of the 2-photon effect—a boost equivalent to reducing pulse width by 96%. Second, we provide image-based evidence that the 2-photon effect occurs at the photoreceptor level. Third, we use our results to compute the specifications for a system that could utilize 2-photon vision and adaptive optics to image and stimulate the retina using a single infrared wavelength and reach luminance levels comparable to conventional displays.
The temporal dynamics of visual information processing varies with the stimulus being processed and with the retinal location that initiates the processing. Here, we present psychophysical data with sub-millisecond resolution showing that visual eccentricity strongly impacts the delay with which stimuli are processed. Even within the central +/-6° of the visual field, we show that processing delays change by up to a factor of approximately three. A simple model, grounded in how retinal physiology changes with eccentricity, provides a quantitative account of the data with one free parameter. The relative delays are on the order of only milliseconds. But if later processing leaves them unresolved, dramatic misperceptions of motion and 3D layout can result. We discuss the implications for how the human visual system solves the temporal binding problem across eccentricity. The results highlight the severe computational challenge of obtaining accurate, temporally-unified percepts of the environment with temporally-staggered processing across the visual field.
We perceive color everywhere and on everything that we encounter in daily life. Color science has progressed to the point where a great deal is known about the mechanics, evolution, and development of color vision, but less is known about the relation between color vision and psychology. However, color psychology is now a burgeoning, exciting area and this Handbook provides comprehensive coverage of emerging theory and research. Top scholars in the field provide rigorous overviews of work on color categorization, color symbolism and association, color preference, reciprocal relations between color perception and psychological functioning, and variations and deficiencies in color perception. The Handbook of Color Psychology seeks to facilitate cross-fertilization among researchers, both within and across disciplines and areas of research, and is an essential resource for anyone interested in color psychology in both theoretical and applied areas of study.
Normal color perception is complicated. But at its initial stage it is relatively simple, since at photopic levels it depends on the activations of just three photoreceptor types: the long‐ (L‐), middle‐ (M‐) and short‐ (S‐) wavelength‐sensitive cones. Knowledge of how each type responds to different wavelengths—the three cone spectral sensitivities—can be used to model human color vision and in practical applications to specify color and predict color matches. The CIE has sanctioned the cone spectral sensitivity estimates of Stockman and Sharpe (Stockman and Sharpe, 2000, Vision Res) and their associated measures of luminous efficiency as “physiologically‐relevant” standards for color vision (CIE, 2006; 2015). These LMS cone spectral sensitivities are specified at 5‐ and 1‐nm steps for mean “standard” observers with normal cone photopigments and average ocular transparencies, both of which can vary in the population. Here, we provide formulae for the three cone spectral sensitivities as well as for macular and lens pigment density spectra, all as continuous functions of wavelength from 360 to 850 nm. These functions reproduce the tabulated discrete CIE LMS cone spectral sensitivities for 2‐deg and 10‐deg with little error in both linear and logarithmic units. Furthermore, these formulae allow the easy computation of non‐standard cone spectral sensitivities (and other color matching functions) with individual differences in macular, lens and photopigment optical densities, and with spectrally shifted hybrid or polymorphic L‐ and M‐cone photopigments appropriate for either normal or red‐green color vision deficient observers.
1. New microspectrophotometric measurements have been made of the photo-pigments of individual rods and cones from the retina of the rhesus monkey (Macaca mulatta). The measuring beam was passed transversely through isolated outer segments. 2. The transverse absorbance for rods ranged from 0.02 to 0.04 and that for cones from 0.01 to 0.03. 3. The mean absorbance spectrum for rods (n = 25) had a peak of 502 +/- 2.7 nm. A digitonin extract from the same group of eyes gave a lambda-max. of 499 +/- 1 nm. 4. Of a sample of 82 cones, 40 were 'red' (P565 nm) and 42 were 'green' (P536 nm). The mean absorbance spectrum for the green cones is very similar to the Dartnall nomogram, but that for the red cones is narrower. 5. No bleachable, blue-sensitive outer segments were recorded, although structures were found that absorbed at short wave-lengths and were neither photosensitive nor dichroic. 6. If the long wave-length and middle wave-length cone pigments of the rhesus monkey are assumed to be identical to those of man and if additional assumptions are made about the lengths of human outer segments and about prereceptoral absorption, it is possible to derive psychophysical sensitivities that closely resemble the pi5 and pi4 mechanisms of W. S. Stiles.
At the 1992 meeting of CIE Committee TC-136, two sets of cone fundamentals were considered; the Smith and Pokorny fundamentals based upon the Judd revised Standard Observer and a set proposed by Stockman and MacLeod based on the mean Stiles 2 deg pilot data.
The purpose of this paper is to familiarize the reader with the fundamentals of photoreceptor optics, defined here as the science that investigates the effects of the optical properties of a photoreceptor, i.e. its size, shape, refractive index, orientation and arrangement, on the absorption of light by photopigment (MILLER, 1974; SNYDER, 1974a). Most photoreceptors of those vertebrates and invertebrates with a high degree of acuity and sensitivity can be described roughly as long narrow cylinders with a diameter comparable to the wavelength of light in the visible, and an index of refraction greater than the surrounding medium. Our general concern here is with the consequences of confining photopigment within such a cylinder.
This paperback reprint of a classic book deals with all phases of light, color, and color vision, providing comprehensive data, formulas, concepts, and procedures needed in basic and applied research in color vision, colorimetry, and photometry.
In the study of receptor optics, the current era originates with the discovery of retinal directional sensitivity by Stiles and Crawford in 1933. In recent years the essential complexities of receptor-optical properties have been revealed.These properties give rise to directional sensitivity, hue, saturation, and resolution changes. They have been employed to separate photopic from scotopic functions, and to indicate the status of receptor-orientation properties. In some patients exhibiting amblyopia or retinal pathology, characteristic disturbances in receptor directional sensitivity have been noted. It is now possible to induce changes in human receptor orientation.Retinal receptors, mitochondria in receptor ellipsoids, and the lamellae and the photosensitive pigment in each lamella of receptor outer segments are orientated. Taper of ellipsoids in retinal cones allows more efficient energy transfer and probably plays an important role in receptor directionality. The configurations, diameters, and indexes of the receptors give rise to the waveguide modal-pattern form of energy transfer. This results in nonuniform distributions of energy in and about receptor outer segments. These distributions and their transmissivity vary within single, and between different retinal receptors as a function of wavelength, and angle of incidence of light. The roles played by these phenomena in vision (particularly the wavelength separation mechanism) require evaluation.
According to Newton's analysis of light, every colour in nature is produced by the mixture, in various proportions, of the different kinds of light into which white light is divided by refraction. By means of a prism we may analyse any coloured light, and determine the proportions in which the different homogeneous rays enter into it; and by means of a lens we may recombine these rays, and reproduce the original coloured light. Newton has also shown how to combine the different rays of the spectrum so as to form a single beam of light, and how to alter the proportions of the different colours so as to exhibit the result of combining them in any arbitrary manner.
Using a new trichromatic colorimeter a series of colour matches through the spectrum has been made by ten observers. The results have been averaged and a mean set of trichromatic coefficients for the spectral colours derived. These results are compared with previous determinations made by König and Abney. The variations in the coefficients that have been found amongst the ten observers must, as a consequence of a new method of basing the trichromatic units, be attributed to variations in the process of reception, but their magnitude appears to be of a small order. On the other hand, there are big differences in the amount of the macular pigment in different eyes and probably some variation in its dominant hue. These variations have been investigated by matches on a standard white, results for 36 observers being given in the paper and a mean value determined. This value, combined with the mean spectral coefficients, has been used to compute an average locus for the spectral colours in the colour triangle, with white at the centre.
Other points discussed in the paper include the technique of colour matching, the range of intensity over which matches remained valid, and variations of luminosity.
The availability of tables with standardized data on the properties of a normal visual visual observer has been a great help in scientific communication. For daily practice these data, going back to the 1920s, still suffice. For basic science they show shortocmings, however. The present paper gives new and extended tables which are intended to be complementary to, rather than to compete with, the old CIE tables.
1.
Measurements have been made of the dark-adapted foveal threshold of normal and colour blind persons in five parts of the spectrum using a 1 circular test field.
2.
Compared to normals, protanopes (red-blinds) show an elevation of the threshold which increases slowly from blue to yellow and rises rapidly thereafter until in the red the threshold is more than ten times as high as normal. Deuteranopes (greenblinds) do not show so high an elevation, their maximum in the green being only about 70% above normal.
3.
These threshold elevations correspond to luminosity losses in the spectrum. For the protanope the total loss in the spectrum is nearly one-half of the normal luminosity; for the deuteranope it is nearly two-fifths of normal.
4.
Measurements were made of the illumination necessary for equal visual performance in normal and colour blind subjects. It was found that protanopes require 119% and deuteranopes 55% more light to achieve a visual acuity of 0.29 reciprocal minutes. These values agree closely with those found in the luminosity measurements.
5.
Such losses support the idea that colour blindness corresponds to the loss of one of the three receptor systems usually postulated to account for normal colour vision. However, the colour sensations reported by colour blind persons, especially monocular colour blinds, do not support the idea of a lost or inactivated receptor system. A fresh explanation for colour blindness is needed to reconcile these conflicting kinds of evidence.
The influence of test field brightness on the results of flicker-photometry has been studied. In the greater part of the measurements a red and a green test field have been compared. Further the influence of a coloured background, on which the test field was superimposed, has been examined. Various normal trichromats, anomalous trichromats and dichromats were observers.It is found that, below 50 photons, simple laws for the photometry are valid. The adjustment of the photometer does not then change if the brightnesses of all components are multiplied by the same factor, or if a background is added. At higher brightness levels deviations occur.
A precise relative optical density spectrum of the macular pigment, based upon its dichroic properties, was determined. The spectrum proved essentially identical to that of liposome-bound zeaxanthin and lutein, a system duplicating the macular pigment and its environment. Substantial agreement was also found with the spectra of Wyszecki and Stiles (1982, Color science: Concepts and methods, quantitative data and formulae. New York: Wiley) and Vos (1972, Institute for Perception, RVO-TNO, IZF 1972-17, Soesterberg, The Netherlands), and the latter is recommended as a standard. For 7 subjects, the pigment density spectrum derived from foveal and extra-foveal sensitivities was compared with the dichroism-based spectrum. Results indicated that the pigment is described by a common distribution of molecular orientations for all subjects.
Summary also in Dutch. Thesis (doctor)--Universiteit van Amsterdam, 1979. Includes bibliographical references (p. 143-147).
In a space where Cartesian coordinates represent the excitations of the three cone types involved in color vision, a plane of constant luminance provides a chromaticity diagram in which excitation of each cone type (at constant luminance) is represented by a linear scale (horizontal or vertical), and in which the center-of-gravity rule applies with weights proportional to luminance.
A comparison was made between the shape of the iodopsin absorption spectrum calculated for appropriate optical density to (1) a set of König-type fundamentals in which the tritanopic copunctal point was set on the alychne and (2) data obtained from red-green dichromats using high intensity heterochromatic flicker procedures which eliminated participation by the short-wavelength sensitive mechanism. The transformation of normal color mixture data resulted in two fundamentals which gave a reasonable prediction of the tritanopic coefficients. The dichromaticHFP data corrected individually to average macular pigment agreed with their respective fundamental above 430 nm. TheHFP data and transformation were converted to a retinal level, quantized and plotted as a function of wavenumber. For the middle-wavelength-sensitive mechanism, the protanopicHFP data and its König-type fundamental agreed with the predicted absorption spectrum above 460 nm. The deviations below 460 nm had the shape of the lens absorbance curve. For the long-wavelength sensitive mechanism, the deuteranopic data and its König-type fundamental agreed with the predicted absorption spectrum above 520 nm. The deviations below 520 nm could not be fit solely by the lens absorbance factor used above, but needed in addition, added macular pigment of optical density at 460 nm ofca. 0.12. This result was checked by calculating predicted tritanopic coefficients for the two predicted absorption spectra, when the long-wavelength sensitive spectrum was screened by a slight amount (o.d. of 0.12 at 460 nm) of macular pigment. These predicted coefficients agreed with the Wright tritanopic coefficients. We conclude (a) that the shape of the iodopsin absorption spectrum provides a reasonable basis for computation of absorption spectra of the middleand long-wavelength sensitive cone pigments and (b) that long-wavelength sensitive cones of deuteranopes. tritanopes, and normal trichromats are subject to a selective screening filter of optical density at 460 nm of 0.12 and spectral shape similar to macular pigment.
Unequal homologous recombination events between green and red cone pigment genes produce the red-green or green-red hybrid pigment genes found in many individuals with variant color vision. Photobleaching difference absorption spectroscopy of hybrid pigments produced in cultured cells shows that the spectral sensitivity of each hybrid pigment is intermediate between the parental green and red pigment sensitivities. Amino acids encoded by exons 2, 3, 4, and 5 produce spectral shifts at the wavelength of maximal absorbance of 0 to 4, 0 to 4, 3 to 4, and 15 to 21 nanometers, respectively, the exact value depending on the identities of amino acids elsewhere in the hybrid.
A precise relative optical density spectrum of the macular pigment, based upon its dichroic properties, was determined. The spectrum proved essentially identical to that of liposome-bound zeaxanthin and lutein, a system duplicating the macular pigment and its environment. Substantial agreement was also found with the spectra of Wyszecki and Stiles (1982, Color science: Concepts and methods, quantitative data and formulae. New York: Wiley) and Vos (1972, Institute for Perception, RVO-TNO, IZF 1972-17, Soesterberg, The Netherlands), and the latter is recommended as a standard. For 7 subjects, the pigment density spectrum derived from foveal and extra-foveal sensitivities was compared with the dichroism-based spectrum. Results indicated that the pigment is described by a common distribution of molecular orientations for all subjects.
Flicker modulation sensitivity measurements made on high intensity orange steady backgrounds indicate that signals from short-wavelength sensitive cones (S-cones) have access to two pathways. At low S-cone adaptation levels the frequency response falls quickly with increasing frequency, but at higher adaptation levels it extends to much higher frequencies. At these higher S-cone adaptation levels, the following procedures can selectively expose either a process sensitive to low frequencies or one more sensitive to higher frequencies:
New action spectra are derived for the foveal cones on the basis of three assumptions: (1) the Stiles-Burch (1959) colorimetric data are better than CIE 1931; (2) the long wavelength flanks of the dichromatic luminosity functions offer better anchorage than the confusion loci; and (3) the relative mutual heights per receptor can be derived from the Bezold-Brücke effect. Since these assumptions do not include photometric data, we could at the end ask how L lambda, M lambda and S lambda combine to V lambda. The best answer appeared to be V lambda = 0.68 L lambda + 0.34 M lambda -0.02 S lambda, reflecting both relative receptor population densities and a negative input of the S-system to luminance.
1. Human short-wave S cone signals are important for colour vision and here we examine whether the S cone signals also contribute to motion and luminance. 2. Detection was measured with moving patterns that selectively stimulated S cones-violet sine-wave gratings of 1 cycle deg-1 on an intense yellowish field. For rates up to 12 Hz, detection was governed by non-directional mechanisms, possibly of a chromatic nature, as shown by three findings: moving gratings had to be suprathreshold for their direction to be identified; the threshold ratio of counterphase flickering versus moving gratings was low; and direction-selective adaptation was essentially absent. 3. Evidence for less sensitive, directional mechanisms includes the following: at high velocity, the direction of movement of the violet gratings can be identified just slightly above the detection threshold; directional adaptation was strong with a suprathreshold test pattern; velocity was seen veridically for clearly suprathreshold patterns; and a counterphase flickering test, added in spatial-temporal quadrature phase to a similar suprathreshold mask, had identical detection and direction-identification thresholds. 4. Interactions of long-wave L cone and S cone signals in direction-selective mechanisms were measured with an orange counterphase grating and a violet counterphase test, both flickering at the same rate and presented in spatial quadrature phase on the yellowish adapting field. Direction identification thresholds, measured as a function of the temporal phase of two gratings, demonstrated both that the S cone signal lags considerably behind the L cone signal (an effect that strongly varies with S cone light adaptation), and more strikingly, the S cone signal summates with a negative sign and thus is effectively inverted in direction-selective mechanisms. 5. Quantitatively similar temporal phase functions were obtained with uniform violet and orange flicker when a luminance discrimination criterion was used: thus the S cone signal summates negatively with the L cone signal for both discrimination of luminance flicker and the direction of motion. 6. The temporal phase functions accurately predicted threshold summation for identifying the direction of motion of a pair of violet and orange gratings moving with the same velocity but with different spatial phase offsets. Once the relative temporal phase lag of the S cones was compensated for, there was linear threshold summation for the violet and orange patterns when presented in effective (physiological) spatial antiphase, and clear cancellation when presented in phase. This and related experiments show a linear summation of S, M and L cone signals for direction detection, with the S cones having a negative sign.(ABSTRACT TRUNCATED AT 400 WORDS)
The method of constant stimuli was used to estimate the psychometric functions for detection of one or two flashes when two light pulses were presented. The test stimulus consisted of two simultaneous 0.5 msec, 1' pulses separated by 17'. Observers reported seeing 0, 1 or 2 flashes. A computer-controlled direct-view apparatus allowed sampling of slightly different foveal locations on each trial. The data were analyzed assuming a binomial probability for sampling of L and M cones and Poisson distributed quantal fluctuation. Under these assumptions, the measurements imply that detection requires a minimum of 5-7 quanta absorbed per cone, and that the effective number of cones illuminated by the 1', 0.5 msec pulse is two. The estimated L/M cone ratio was 1.6 for one observer and 4.0 for the other; each observer's ratio was in general agreement with the value estimated independently by heterochromatic flicker photometry.
The determination of the relative numbers of different cone types in the human retina is fundamental to our understanding of visual sensitivity and color vision; yet direct measurement which provide this basic information have not previously been made for all cone types. Here we present a model which links the detection of a test light of small dimension to the number of cones contributing to detection of the light. We selectively isolated either the long-wavelength-sensitive (L) or the middle-wavelength-sensitive (M) cones, by choosing combinations of wavelengths of adapting backgrounds and tests to favor detection by the cone class of interest. Our model was applied to the detection functions measured for six color normal observers to obtain estimates of the relative numbers of L to M cones. Our estimates ranged between 1.46 and 2.36 for our observers with a mean value near two L cones for every M cone in human fovea centralis.
Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA
clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent
identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the
blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene,
are proposed to reside in a head-to-tail tandem array within the X chromosome.
1. Spectral sensitivities of cones in the retina of cynomolgus monkeys were determined by recording photocurrents from single outer segments with a suction electrode. 2. The amplitude and shape of the response to a flash depended upon the number of photons absorbed but not the wave-length, so that the 'Principle of Univariance' was obeyed. 3. Spectra were obtained from five 'blue', twenty 'green', and sixteen 'red' cones. The wave-lengths of maximum sensitivity were approximately 430, 531 and 561 nm, respectively. 4. The spectra of the three types of cones had similar shapes when plotted on a log wave number scale, and were fitted by an empirical expression. 5. There was no evidence for the existence of subclasses of cones with different spectral sensitivities. Within a class, the positions of the individual spectra on the wave-length axis showed a standard deviation of less than 1.5 nm. 6. Psychophysical results on human colour matching (Stiles & Burch, 1955; Stiles & Burch, 1959) were well predicted from the spectral sensitivities of the monkey cones. After correction for pre-retinal absorption and pigment self-screening, the spectra of the red and green cones matched the respective pi 5 and pi 4 mechanisms of Stiles (1953, 1959).