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PubMed1985

Cone mechanisms underlying the color discrimination of deutan color deficients.

An alternation method of color matching was used to obtain a series of extended Rayleigh matches from several deutan color deficients with varying degrees of color discrimination. With large stimulus fields there were differences in the matches made by observers with good color discrimination and the matches made by observers with poor color discrimination. The matches made by observers with poor discrimination could not be modeled with normal cone action spectra. When the field size was reduced the matches of all observers were quite similar and could be modeled with two cone action spectra that were normal in shape and separated by approximately 5 nm. Results suggest that individual differences in ability to discriminate color among deutan observers are not solely related to differences in the cone action spectra.

Adolescent↗

PubMed1977

Perceptual load in searching for sloping colored lines camouflaged by colored backgrounds: a separate-groups investigation.

Altogether 168 men searched briefly for colored sloping lines embedded in a background of random color. Using a separate-groups experimental design, search for six kinds of target was found to be less effective after practice than search for a single kind of target. Reducing the number of colors of targets from three to one was considerably more beneficial than reducing the number of main directions of slope from two to one. Reducing the number of kinds of target without reducing the number of relevant stimulus values was also found to improve the effectiveness of search, but search was even more effective when the number of relevant stimulus colors was reduced. The results can be predicted from the total number of selection operations required. However, a more precise fit needs to reflect the considerably greater difficulty of searching for a number of directions of slope. When targets were poorly camouflaged, search was equally effective whether there were four colors or only a single color of target to search for.

Adolescent↗

PubMedDate not supplied

Using a computer color-matching system in color reproduction of porcelain restorations. Part 1: Application of CCM to the opaque layer.

The reproduction of natural tooth color using porcelain restorations is quite cumbersome, for it is difficult to select, communicate, reproduce, and evaluate color objectively. The present process of color reproduction lacks precision and is primarily dependent on the individual efforts and abilities of the dentist and ceramist. The computer color-matching system, aided by a spectrophotometer and computer, can be an excellent method for reproducing specific colors of various objects. This paper reports application of the system to reproduce various opaque colors used for metal ceramic restorations.

Color↗

PubMed1976

An acquired color defect of the opponent-color system.

An acquired unilateral color defect in a 22-year-old man has been investigated with standard clinical tests and by using techniques which, it is thought, test specifically for the sensitivity of the luminance and opponent-color systems. The spectral sensitivity of the defective left eye, using 1 degree 200 ms. test flashes on a white background, has a single broad peak at about 550 nm. and resembles the photopic luminosity curve; in contrast, the normal curve, measured in the same conditions, has three peaks at about 440, 520, and 600 nm. However, the subject's spectral sensitivity curve for detecting 20 Hz. flicker is quite normal and is similar to his curve for 200 ms. flashes. It has recently been proposed that the three peaks of the normal curve for 200 ms. flashes reflect the activity of the opponent-color system, whereas the single peak for flicker detection is related to the luminance system. The preceding observations may thus be interpreted in terms of a specific loss of the subject's opponent-color system and this would explain his poor color discrimination. His luminance system appears to be normal, and evidence is presented for the maintained function of red- and green-sensitive (but not blue-sensitive) cones. The spectral sensitivity of the subject's right eye is nearly normal, suggesting a precortical origin of the defect; however, there seems to be some abnormality in this eye, indicating a less developed form of the same defect.

Adult↗

PubMed1991

Effects of color CRT display on pupil size in color-blind subjects.

The effects of color cathode ray tube (CRT) display on the pupil size in color-blind subjects were studied experimentally. Red, magenta, green, cyan, yellow, and white were presented on the CRT. Five protan subjects, five deutans, and five normal subjects were tested using infrared pupillography. In the protan group, the pupils were significantly less sensitive to red (wavelength: 600 nm) targets compared to the other colors. In the deutans and the control group, there were non-significant changes in pupil size in response to the colors. Dominant wavelengths above 600 nm in color CRTs should be avoided in routine work presentation because of less sensitivity in protanopias.

Adult↗

PubMed1988

[Study of color perception using a new color test and desaturated panel D 15 in normal subjects and diabetics].

The authors used two tests (the Lanthony's New Color Test and the desaturated Panel D 15 test) to evaluate color vision in 235 subjects (235 eyes) of which 80 normal and 155 diabetic (85 with background retinopathy and 70 without retinopathy, as demonstrated by fluorescein angiography). The diabetic patients with maculopathy or macular oedema, with mixed or proliferative retinopathy, or with any form of advanced degenerative retinopathy were excluded from this study. The New Color Test was performed in accordance with Lanthony's standardized method, applying only the separation phase (to quantifying the color perception defect, if any) in photopic illuminance conditions at 250 lux. The desaturated Panel D 15 (qualitative classification test) has been performed at illuminance of 500 lux. Both normal and diabetic subjects were divided into two age groups (below and above 45 years) and the discriminatory value of two tests has been assessed in relation to age, diabetes and background retinopathy. The New Color Test showed a highly significant difference between normal subjects and diabetics of comparable age with background retinopathy. There was also a highly significant difference between diabetics with and without retinopathy. On the other hand, the difference between normal subjects and diabetics without retinopathy proved significant in the below-45 age group and no-significant in the above-45 age group. The results obtained in the desaturated Panel D 15 test have been similar: below the 45 years of age all differences among the three subject groups proved significant, whereas in the above-45 age group no significant differences were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Color categorization and color constancy in a neural network model of V4.

We develop a neural network model that instantiates color constancy and color categorization in a single unified framework. Previous models achieve similar effects but ignore important biological constraints. Color constancy in this model is achieved by a new application of the double opponent cells found in the "blobs" of the visual cortex. Color categorization emerges naturally, as a consequence of processing chromatic stimuli as vectors in a four-dimensional color space. A computer simulation of this model is subjected to the classic psychophysical tests that first uncovered these phenomena, and its response matches psychophysical results very closely.

Animals↗

PubMed1987

Retinal inputs to the geniculate relay cells in the eastern chipmunk (Tamias sibiricus asiaticus): a comparison between color and non-color sensitive cells.

Single unit recordings were made from the relay cells of the lateral geniculate nucleus in the eastern chipmunk. Of 362 relay cells, 47 cells (13%) were classified as color sensitive and the rest as non-color sensitive cells. Non-color sensitive cells were further classified into 5 subclasses: off-phasic, on-phasic, on-off-phasic, on-tonic and uncommon types. Within the color sensitive cells there were 3 subclasses; blue excited and green inhibited (+B-G), blue inhibited and green excited (-B+G), and blue excited (+B) cells. Retinal afferents to color sensitive relay cells had the following characteristics: ganglion cells of their origin were distributed in the central high density areas of the retina and axonal conduction velocities were in the intermediate range, though they were somewhat slow in +B cells.

Animals↗

PubMed1991

Temporal differences between color pathways within the retina as a possible origin of subjective colors.

We propose a model of temporal signal processing within the retina based on temporal differences between the color pathways which may explain the phenomenon of subjective color. We quantify the model by inferring impulse response functions from physiological data, and predict the output of the different color pathways to temporally modulated achromatic signals which produce the sensation of color. Certain achromatic temporally modulated signals create imbalances between the color pathways which are analogous to those produced by stationary chromatic signals.

Color Perception↗

PubMed1990

Image segmentation by object color: a unifying framework and connection to color constancy.

A unifying framework is presented for algorithms that use the bands of a multispectral image to segment the image at material (i.e., reflectance) boundaries while ignoring spatial inhomogeneities incurred by accidents of lighting and viewing geometry. The framework assumes that the visual stimulus (image field) from a uniformly colored object is the sum of a small number of terms, each term being the product of a spatial and a spectral part. Based on this assumption, several quantities depending on the reflected light can be computed that are spatially invariant within object boundaries. For an image field either from two light sources on a matte surface or from a single light source on a dielectric surface with highlights, the invariants are the components of the unit normal to the plane in color space spanned by the pixels from the object. In some limited cases the normal to the plane can be used to estimate spectral-reflectance parameters of the object. However, in general the connection of color-constancy theories with image segmentation by object color is a difficult problem. The concomitant constraints on segmentation and color-constancy algorithms are discussed in light of this fact.

Algorithms↗

PubMed1989

Note on color preference and color vision test performance.

The incidence of color deficient vision was investigated using the Pseudo-Isochromatic Plates on a relatively large and representative group. In the sample of 112 adults aged 20 to 80 yr. and comprised of 53% women and 12% minorities, 8% of men and 3% of women were color deficient. Over-all performance indicated no effects for sex or race. Nearly half of the plates were nondiscriminating among sex, minority/majority, and "normal" and "defective" color vision groups. Named color preferences within the "normal" group strongly favored blues and reflected no sex differences.

Adult↗

PubMed1990

Doppler color flow in echocardiography: analytical and in-vitro investigations of the quantitative relationship between orifice flow and color jet dimensions.

The goal of this investigation was to explore the relationship between orifice flow rate and the dimensions of the resulting color jet. Equations were derived which describe flow rate as a function of the color jet dimensions, instrument characteristics, and a coefficient which represents the unknown velocity profile across the jet. Experiments in which fluid was injected at a variety of flow rates via an assortment of orifice sizes into a compliant, axisymmetric chamber were performed for comparison with the analytical results. During each injection, orifice flow rate and color jet dimensions were recorded. The experimental results were closely predicted (r = 0.97) by an equation which expresses flow rate as a function of the ratio of the color jet area and color jet length, and with a coefficient which approximates that of a parabolic velocity profile.

Blood Flow Velocity↗

PubMed1987

Color discrimination and neural coding in color deficients.

Rayleigh color match ranges obtained from color deficient observers varied considerably as a function of spatial and temporal parameters of stimulus presentation. The results suggest that color discrimination losses in color deficients result from abnormalities in the spatial and temporal properties of neural coding in addition to cone photopigment abnormalities.

Color Perception↗

PubMed1991

The use of the Lanthony New Color Test in determining the effects of aging on color vision.

The primary purpose of this study was to collect data on the loss of color vision as a function of age. The Lanthony New Color Test (NCT), which measures acquired losses of color vision in the dimensions of hue, saturation, and brightness, was used to compile data on 68 subjects. The minimum number of subjects were 10 per decade from age 30 to 90 years. An age gradient of selective loss of discrimination of saturation beginning at age 50 was demonstrated, with rapid change noted after age 60. Similar findings were seen for hue but were not evident for brightness. By age 70, a neutral zone emerged at blue/purple, Munsell chroma level 2. The instrument was shown to be reliable and valid in comparison to the Farnsworth Dichotomous Panel D.15. It is seen that this information will provide a basis for planning safer, more functional environments for elderly people.

Adult↗

PubMed1978

Color analysis of dextrose solutions using a color difference meter.

A method for quantitating color measurements in dextrose solutions by using a color difference meter is described. This method was shown to correlate well with standard American Public Health Association (APHA) color measurements. A mathematical relationship was developed relating yellowness index values to APHA numbers as described in the USP for dextrose solutions. This relationship was tested by comparing the results from standard APHA color tests on laboratory samples of autoclaved dextrose solutions to APHA numbers calculated from yellowness index values for the same samples.

Color↗

PubMed1988

Positive colored afterimages from the figure-ground configurations of colored lights: effects of chromaticity, luminance and a spatial parameter of the adapting stimuli.

Colored afterimages were obtained after the eye was exposed to the adapting field consisting of the figure-ground configuration of colored lights with the same hue and different saturation. When a colored patch was surrounded by a more saturated field, the color of the afterimage was similar to that of the previous patch (positive afterimage). By measuring the threshold chromaticity difference between the patch and the surround for the production of the positive afterimage, the effects of the chromaticity, luminance and a spatial parameter of the adapting field were determined. The obtained threshold chromaticity differences increased with an increase in the saturation of the adapting field, and with a decrease in the surround luminance. When the adapting field consisted of an equiluminous saturation-modulated rectangular grating, the threshold chromaticity difference curves showed similar properties as those of the contrast thresholds for equiluminous chromaticity-modulated gratings. The results suggest the existence of a set of mechanisms at higher-order level in the visual system, tuning the difference in hue and/or saturation across contours.

Adaptation, Ocular↗

PubMed1986

Conjunction of color and form without attention: evidence from an orientation-contingent color aftereffect.

According to feature-integration theory (Treisman & Gelade, 1980), separable features such as color and shape exist in separate maps in preattentive vision and can be integrated only through the use of spatial attention. Many perceptual aftereffects, however, which are also assumed to reflect the features available in preattentive vision, are sensitive to conjunctions of features. One possible resolution of these views holds that adaptation to conjunctions depends on spatial attention. We tested this proposition by presenting observers with gratings varying in color and orientation. The resulting McCollough aftereffects were independent of whether the adaptation stimuli were presented inside or outside of the focus of spatial attention. Therefore, color and shape appear to be conjoined preattentively, when perceptual aftereffects are used as the measure. These same stimuli, however, appeared to be separable in two additional experiments that required observers to search for gratings of a specified color and orientation. These results show that different experimental procedures may be tapping into different stages of preattentive vision.

Adolescent↗

PubMed1988

Color Doppler flow mapping in patients with coarctation of the aorta: new observations and improved evaluation with color flow diameter and proximal acceleration as predictors of severity.

We performed color Doppler flow mapping in 15 patients, 1 week to 17 years old (mean 42 months), with coarctation of the aorta that was confirmed subsequently by angiography and/or surgery. Twelve patients had native coarctation and three had mild recoarctation after surgical repair. Color Doppler flow maps were analyzed with a digital analysis package and a Sony computer system. The diameter in the region of coarctation from the color Doppler flow map (mean = 2.0 +/- 0.8 mm [SD]) correlated well with the coarctation diameter measured at angiography (mean = 1.8 +/- 0.8 mm; r = .83, SEE 0.43 mm) in the 10 patients with native coarctation undergoing angiography, but the coarctation diameter measured by two-dimensional echocardiography (3.9 +/- 1.5 mm) was poorly predictive of the angiographic severity (r = .23). Additionally, spatial acceleration was seen in all patients proximal to the coarctation site, with an aliased and accelerating stream narrowing progressively as it proceeded toward the coarctation site, a pattern that is not seen in healthy subjects. Computer analysis of the color Doppler images provided pseudo three-dimensional and digital velocity maps for blue, red, and green (turbulent) flow velocities to allow an enhanced appreciation of the accelerating stream, easily separating this from normal descending aortic aliasing patterns. The narrowing of the acceleration area in the proximal descending aorta (distal/proximal acceleration zone ratio) was also predictive of the angiographic severity of coarctation (r = .83). The distribution of low-level turbulence seen proximally paralleled the distribution of the proximal accelerating stream.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗