scholarly journals A study of unusual Rayleigh matches in deutan deficiency

2008 ◽  
Vol 25 (3) ◽  
pp. 507-516 ◽  
Author(s):  
J.L. BARBUR ◽  
M. RODRIGUEZ-CARMONA ◽  
J.A. HARLOW ◽  
K. MANCUSO ◽  
J. NEITZ ◽  
...  
Keyword(s):  
Optical Density ◽  
Model Parameters ◽  
Noise Amplitude ◽  
Color Channel ◽  
Green Color ◽  
Cone Pigments ◽  
Cone Photopigments ◽  
Peak Sensitivity ◽  
Color Deficiency ◽  
Hybrid Genes

Rayleigh match data were modeled with the aim of explaining the locations of match midpoints and matching ranges, both in normal trichromats and in subjects with congenital color deficiency. Model parameters included the wavelength of peak sensitivity of cone photopigments, the effective photopigment optical density, and the noise amplitude in the red-green color channel. In order to avoid the suprathreshold, perceptual effects of extreme L:M cone ratios on color vision, selective post-receptoral amplification of cone signals is needed. The associated noise is also amplified and this causes corresponding changes in red-green threshold sensitivity. We propose that the noise amplitude and hence the size of the matching range in normal trichromats relates to the known inter-subject variation in the relative numbers of L and M cones. If this hypothesis can be shown to account for the extremes of the red-green matching range measured in normal trichromats, it is of interest to establish the extent to which it also predicts the unexpected, small matching ranges that are observed in some subjects with red-green color deficiency. A subset of subjects with deutan deficiency that exhibited less common Nagel matches were selected for genetic analysis of their cone pigment genes in order to confirm the type of deficiency, and to predict the corresponding peak wavelength separation (δλmax) of their two, long-wavelength cone pigments. The Rayleigh match model predicted accurately the midpoint and the range for the spectral differences specified by the genes. The prediction also required plausible selection of effective optical density of the cone pigments and noise. The noise needed varied, but the estimates were confined to lie within the limits established from the matching ranges measured in normal trichromats. The model predicts correctly the small matching ranges measured in some deuteranomalous subjects, principally accounted for by a low estimate of noise level in the red-green channel. The model also predicts the “normal” matches made by some subjects that rely on two hybrid genes and therefore exhibit red-green thresholds outside the normal range, typical of mild deuteranomaly.

On the use of red stimuli to isolate magnocellular responses in psychophysical experiments: A perspective

2004 ◽  
Vol 21 (1) ◽  
pp. 63-68 ◽  
Author(s):  
BERNT CHRISTIAN SKOTTUN
Keyword(s):  
Present Report ◽  
Red Light ◽  
The Other ◽  
Green Color ◽  
Green Filter ◽  
Blue Filter ◽  
Parvocellular System ◽  
Cone Pigments ◽  
Parvocellular Neurons ◽  
Psychological Experiments

Neurophysiological recordings have shown that activity of magnocellular neurons may be reduced by red backgrounds. This has led some researchers to use red light, or red filters, in attempts to determine the magnocellular contribution to psychophysical tasks. This requires that red light not affect parvocellular neurons, or at least that it is possible to control for the effect on the parvocellular system by using other colors. The present report investigates these assumptions by calculating the effect of red, green, and blue filters on the three cone pigments and on the four parvocellular color-opponent cell mechanisms. It is found that a red filter has a large effect on the long- and middle-wavelength cone pigments and on the red–green color-opponent mechanisms. A green filter, on the other hand, has little effect. A blue filter has a fairly pronounced effect but this effect is distinctly different from that of the red filter. These results indicate that one ought not rely upon red light to isolate magnocellular activity in psychological experiments. The results also indicate that it is difficult to use colors other than red to control for the effect of this color on the parvocellular system.

scholarly journals Modelling the Rayleigh match

2004 ◽  
Vol 21 (3) ◽  
pp. 477-482 ◽  
Author(s):  
P.B.M. THOMAS ◽  
J.D. MOLLON
Keyword(s):  
Absorption Spectra ◽  
Optical Density ◽  
Field Size ◽  
General Behavior ◽  
Anticlockwise Rotation ◽  
Peak Sensitivity ◽  
The Individual ◽  
Unique Match

We use the photopigment template of Baylor et al. (1987) to define the set of Rayleigh matches that would be satisfied by a photopigment having a given wavelength of peak sensitivity (λmax) and a given optical density (OD). For an observer with two photopigments in the region of the Rayleigh primaries, the observer's unique match is defined by the intersection of the sets of matches that satisfy the individual pigments. The use of a template allows us to illustrate the general behavior of Rayleigh matches as the absorption spectra of the underlying spectra are altered. In a plot of the Y setting against the red–green ratio (R), both an increase in λmax and an increase in optical density lead to an anticlockwise rotation of the locus of the matches satisfied by a given pigment. Since both these factors affect the match, it is not possible to reverse the analysis and define uniquely the photopigments corresponding to a specific Rayleigh match. However, a way to constrain the set of candidate photopigments would be to determine the trajectory of the change of match as the effective optical density is altered (by, say, bleaching or field size).

Visual Pigments and Molecular Genetics of Color Blindness

Physiology ◽  
1998 ◽  
Vol 13 (2) ◽  
pp. 63-69
Author(s):  
J. K. Bowmaker
Keyword(s):  
Molecular Genetics ◽  
Recombinant Expression ◽  
Color Blindness ◽  
Visual Pigments ◽  
Site Directed Mutagenesis ◽  
Spectral Information ◽  
Directed Mutagenesis ◽  
Green Color ◽  
Hybrid Genes

Red/green color blindness, found in ~1 in 15 men, is caused by the expression of hybrid genes coding for visual pigments. Spectral information from site-directed mutagenesis and recombinant expression has led to the possibility of correlating individual genotypes with psychophysical measurements of the severity of the deficiency.

Four cone pigments in women heterozygous for color deficiency

1981 ◽  
Vol 71 (6) ◽  
pp. 719 ◽  
Author(s):  
Allen L. Nagy ◽  
Donald I. A. MacLeod ◽  
Nicholas E. Heyneman ◽  
Alvin Eisner
Keyword(s):  
Cone Pigments ◽  
Color Deficiency

scholarly journals Scalable Methodology to Hide Audio Data in Cover Image using RGB and Gray Color based Key Positioning Image Steganography

2019 ◽  
Vol 8 (3) ◽  
pp. 7674-7679
Keyword(s):  
Color Image ◽  
Least Significant Bit ◽  
Major Area ◽  
Color Channel ◽  
Green Color ◽  
Replacement Algorithm ◽  
Audio Data ◽  
Positioning Algorithm ◽  
The Given

This objective of this paper is primarily focused on RGB color and Gray scale color based key positioning steganography which has been used to overcome the disadvantages of the Least Significant Bit replacement algorithm and helps to embed the audio data in the color images. The given audio data of various sizes is used to embed in the green color channel of the 24 bit color image sequentially by the key based LSB positioning algorithm. Here the audio threshold is another major area where the focus has been laid as increasing the size of the audio data[26] which can be sent through an image without losing the quality of the audio. This method of hiding the audio data through an image helps to authenticate the sender[25] and verifies whether the data has been really sent to the valid user or is used to prevent morphed secret details by the attacker in the middle. The proposed algorithm has been tested against various existing algorithm to study how effectively the algorithm is working, and how effectively it overcomes the drawbacks of the present algorithms. The algorithm is scalable to serve the purpose of authenticating the different demographical region users living all over world and also to identify that the message is reaching only to the valid user[31].

scholarly journals Perception of color emotions for single colors in red-green defective observers

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2751 ◽  
Author(s):  
Keiko Sato ◽  
Takaaki Inoue
Keyword(s):  
Regression Analysis ◽  
Naming Task ◽  
Color Naming ◽  
Rating Task ◽  
Normal Vision ◽  
Green Color ◽  
Normal Individuals ◽  
Human Color Vision ◽  
Color Deficiency ◽  
Color Emotion

It is estimated that inherited red-green color deficiency, which involves both the protan and deutan deficiency types, is common in men. For red-green defective observers, some reddish colors appear desaturated and brownish, unlike colors seen by normal observers. Despite its prevalence, few studies have investigated the effects that red-green color deficiency has on the psychological properties of colors (color emotions). The current study investigated the influence of red-green color deficiency on the following six color emotions: cleanliness, freshness, hardness, preference, warmth, and weight. Specifically, this study aimed to: (1) reveal differences between normal and red-green defective observers in rating patterns of six color emotions; (2) examine differences in color emotions related to the three cardinal channels in human color vision; and (3) explore relationships between color emotions and color naming behavior. Thirteen men and 10 women with normal vision and 13 men who were red-green defective performed both a color naming task and an emotion rating task with 32 colors from the Berkeley Color Project (BCP). Results revealed noticeable differences in the cleanliness and hardness ratings between the normal vision observers, particularly in women, and red-green defective observers, which appeared mainly for colors in the orange to cyan range, and in the preference and warmth ratings for colors with cyan and purple hues. Similarly, naming errors also mainly occurred in the cyan colors. A regression analysis that included the three cone-contrasts (i.e., red-green, blue-yellow, and luminance) as predictors significantly accounted for variability in color emotion ratings for the red-green defective observers as much as the normal individuals. Expressly, for warmth ratings, the weight of the red-green opponent channel was significantly lower in color defective observers than in normal participants. In addition, the analyses for individual warmth ratings in the red-green defective group revealed that luminance cone-contrast was a significant predictor in most red-green-defective individuals. Together, these results suggest that red-green defective observers tend to rely on the blue-yellow channel and luminance to compensate for the weak sensitivity of long- and medium-wavelength (L-M) cone-contrasts, when rating color warmth.

scholarly journals Visual Pigments of Goldfish Cones

1974 ◽  
Vol 63 (3) ◽  
pp. 279-304 ◽  
Author(s):  
Ferenc I. Hárosi ◽  
Edward F. MacNichol
Keyword(s):  
Absorption Band ◽  
Oscillator Strength ◽  
Optical Density ◽  
Visual Pigment ◽  
Visual Pigments ◽  
Main Absorption Band ◽  
Dichroic Ratio ◽  
Outer Segments ◽  
Retinal Photoreceptors ◽  
Cone Pigments

Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene2 is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra.

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