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PubMed2006

Illusory color mixing upon perceptual fading and filling-in does not result in 'forbidden colors'.

A retinally stabilized object readily undergoes perceptual fading. It is commonly believed that the color of the apparently vanished object is filled in with the color of the background because the features of the filled-in area are determined by features located outside the stabilized boundary. Crane, H. D., & Piantanida, T. P. (1983) (On seeing reddish green and yellowish blue. Science, 221, 1078-1080) reported that the colors that are perceived upon full or partial perceptual fading can be 'forbidden' in the sense that they violate color opponency theory. For example, they claimed that their subjects could perceive "reddish greens" and "yellowish blues." Here we use visual stimuli composed of spatially alternating stripes of two different colors to investigate the characteristics of color mixing during perceptual filling-in, and to determine whether 'forbidden colors' really occur. Our results show that (1) the filled-in color is not solely determined by the background color, but can be the mixture of the background and the foreground color; (2) apparent color mixing can occur even when the two colors are presented to different eyes, implying that color mixing during filling-in is in part a cortical phenomenon; and (3) perceived colors are not 'forbidden colors' at all, but rather intermediate colors.

Adult↗
PubMedDate not supplied

New color vision tests to evaluate faulty color recognition.

PURPOSE: To develop and assess new color vision tests to be used in evaluating faulty color recognition. METHODS: We developed new color vision tests to evaluate faulty color recognition. The two types of color vision tests, designed to assess faulty color recognition in color vision deficiencies, are based on principles that are different from those of the conventional color vision tests. In the first test plate, the subject is asked to choose either a red, green, or gray line from among 10 lines that are randomly colored red, green, gray, yellow, or blue. The score is the difference between the number of correct answers and the number of incorrect answers. In the second test plate, the subject is asked to identify a total of 10 red azalea blossoms, which are dispersed among numerous green leaves. Seventy-five persons with congenital color deficiencies and 20 subjects with normal color vision were examined using these new test plates. RESULTS: The scores differed significantly between dichromats and anomalous trichromats, and between anomalous trichromats and subjects with normal color vision. CONCLUSIONS: The new tests are easy to use, sensitive, and have good reproducibility for use in discriminating subjects with color vision anomalies. These tests reveal the faulty color recognition that occurs unconsciously in persons with color deficiencies, and are useful in judging the quantification of color vision required in their daily life and occupations.

Adolescent↗
PubMed2003

Color change and color-dependent behavior in response to predation risk in the salamander sister species Ambystoma barbouri and Ambystoma texanum.

Although many organisms show multiple types of trait responses to predation risk (e.g., shifts in behavior, morphology, color, chemistry or life history), relatively few studies have examined how prey integrate these multiple responses. We studied the joint expression of color and behavioral responses to predation risk in two sister species of salamander larvae that live in habitats with different selection pressures. We examined responses to predation risk in three situations that differed in availability of refuge and substrate color heterogeneity, and thus availability of behavioral options for reducing risk. Relative to Ambystoma texanum, A. barbouri larvae were darker in color and showed a greater range of color change. With no variation in background color or refuge available, both species exhibited color change to better match the available background. The degree of color change showed by both species, however, did not depend on predation risk. Given the option to choose between light and dark substrates, A. texanum exhibited behavioral background matching (i.e., they preferred substrates that matched their own body color), while A. barbouri's substrate preferences did not depend on their initial body color. Instead, A. barbouri responded to risk by showing a strong preference for dark substrates, followed by a change to a darker body color. With refuge available, A. texanum's refuge use was color-dependent; larvae that were well camouflaged spent less time in refuge. In contrast, A. barbouri showed strong refuge use in response to risk, regardless of their body color. Overall, these results reflect how conflicting selection pressures (predation risk, habitat ephemerality, risk of UV damage) and species differences in mean color and ability to change color can govern the interplay of complementary and compensatory behavioral and color responses to predation risk.

Adaptation, Physiological↗
PubMed1989

[Chromatic study of composite resins. Report 1. The influence of the color measuring instruments and the background colors on the chromatic values].

The purpose of this study was to investigate the influence of the structural difference of the color measuring instruments and the background colors on the chromatical values of the composite resins. Composite resin disks which were 10 mm in diameter and 1 mm and 2 mm in thickness, and made by the light-cured composite resin Silux Plus (3M Co.) were chromatically measured. The colors of the composite resin used in this study were universal, yellow, dark-yellow and light. The color measuring instruments used in this study were the Murakami Color Research Laboratory Fast Spectrophotometer CMS-500 used with the Flexible Sensor FS-1, FS-2 and FS-3, and the Murakami Color Research Laboratory Color Difference Meter CD-270 used with the Improved Light Guide CD-270. The diameters of the head which receives the light from the object were: FS-1 (2 mm), FS-2 (3 mm), FS-3 (5 mm) and Improved Light Guide CD-270 (2 mm). The chromatical values of the resin specimens were measured without back color, backed by a white plate and backed by a black plate. The chromatical values of the composite resin disks were measured with the different color measuring instruments under the different background colors. The XYZ, L*a*b* and xy values were compared and the following results were obtained. 1) The chromatical XYZ, L*a*b* and xy values of the composite resins showed different value patterns among the color measuring instruments. 2) Different influences of the background colors on the chromatical values of the composite resins were obtained among the different colors and different thicknesses of the resins in the cases of some color measuring instruments were used. 3) The most precise color measuring instrument for chromatical measuring of the composite resins among the instruments used in this study was the Fast Spectrophotometer CMS-500 used with the FS-3. 4) Prior to the comparison of the chromatical values measured by the different color measuring instruments, the chromatical values obtained by measurement with the same specimens should be compared and the structural differences, the precision and the sensitivities of the instruments should be understood.

Color↗
PubMed2004

[Investigation of color vision using a web-based color vision test].

BACKGROUND: Screening tests of visual functions using the Internet are theoretically possible. To use these tests as a screening test, they must deliver comparable results with conventional test procedures. A web-based color vision test was developed based on pseudoisochromatic color plates. METHOD: The web-based color vision test was developed according to the pseudoisochromatic color plates by Velhagen and Broschmann using the programming-languages HTML, Java, and Perl. Sixty-five voluntary subjects, including nine color-deficient subjects, were examined by luminescence color plates (via web-based color vision test) and pigment color plates (via book). The statistical analysis was performed by determining the correspondence and the 95%-confidence interval. RESULTS: The correspondence of the test results for all subjects was 0.98 and the 95%-confidence interval was within 0.91 and 0.99. The correspondence of the test results in the group of color-deficient subjects was 1.0 and because of the limited number the 95%-confidence interval was within 0.71 and 1.0. CONCLUSIONS: The web-based color vision test with luminescence color plates for color-efficient and color-deficient subjects delivers test results comparable to pigment color plates under standardized examination conditions. Further studies are needed to examine if the web-based color vision test can also be used as an Internet screening test.

Adult↗
PubMed2004

Color Doppler velocimetry and three-dimensional color power angiography of cervical carcinoma.

OBJECTIVES: To investigate the blood flow within invasive cervical carcinoma by transvaginal two-dimensional (2D) color spectral Doppler and three-dimensional (3D) color power angiography and to correlate these parameters with the clinicopathological characteristics. METHODS: Seventy-four patients with invasive cervical carcinoma were enrolled for the analysis. Squamous cell carcinoma serum antigen levels (SCC) were obtained for all the patients. Sections of all malignant tissues were analyzed for tumor expression of cyclooxygenase-2 (COX-2). All patients underwent color and spectral Doppler examination and 44 patients had 3D color power angiography. Color spectral Doppler parameters (color score, lowest resistance index (RI), highest peak systolic velocity (PSV)) and 3D color power angiography indices (relative color, average color, flow measure) of FIGO I/II cervical cancers were compared with those obtained in a control group of 24 patients with a normal uterine cervix. Pulsed Doppler parameters and the 3D vascular indices were compared with clinicopathological parameters, SCC serum antigen levels and tumor COX-2 expression. RESULTS: At color Doppler analysis 72 patients (97%) showed intralesional detectable vessels. Color spectral Doppler and 3D-derived parameters were significantly different in FIGO I/II cervical cancers compared with those in women with a normal cervix. A significantly higher color score (P = 0.0008), lower RI (P = 0.032) and higher PSV (P = 0.004) were associated with a tumor diameter > or =4 cm compared with smaller tumors. The highest PSV was significantly higher in patients with FIGO stage III/IV compared with FIGO stage I/II (P = 0.0069). There was a direct correlation between PSV and SCC (r = +0.44, P = 0.003). The median relative color was significantly higher in patients with a higher color score (P = 0.0006). No statistically significant correlations were found between 3D color power angiography parameters and the clinicopathological characteristics or between the 3D vascular parameters and biological factors. CONCLUSIONS: Alterations of 3D ultrasound-derived vascular indices were found in patients with cervical cancer compared with those with a normal cervix. Moreover, some vascular indices proved to be associated with tumor size. The assessment of a possible clinical role of 2D and 3D ultrasound-derived vascular indices in cervical cancer deserves further investigation.

Adult↗
PubMed1985

Color contrast perimetry. The spatial distribution of color defects in optic nerve and retinal diseases.

Color contrast perimetry was used to evaluate central visual field defects in a group of 28 patients with visual loss resulting from optic nerve or retinal diseases. Kinetic perimetry was performed using colored test objects of constant luminance, equated to a white surround of 10 ft lamberts. Colored test objects were varied in size and in extent of color saturation. Test object color saturation was varied from a white that matched the color and luminance of the adapting background toward either the blue or the red color maxima of a video tangent screen. All central visual field defects that were demonstrable by luminance contrast perimetry were also detected by color contrast testing, and no defects were found for color contrast detection that could not also be demonstrated by conventional luminance increment perimetry. Retinal diseases usually produced scotomas for both color and luminance contrast detection, while optic nerve disorders tended to produce global depressions of both color and luminance contrast sensitivity across the entire visual field in addition to scotomas. There was no systematic difference in visual field defects for either class of disease when comparing color contrast in the blue (tritan) versus the red (protan) axes of color space. The apparent tritan or protan/deutan axes of color confusion found by hue discrimination testing in acquired dyschromatopsias may be determined by the relative spatial distribution of defects in the central visual field rather than by selective impairment of neural mechanisms for color or luminance information processing.

Adult↗
PubMed1999

Evaluation of a new color vision test: "color vision testing made easy".

PURPOSE: A new pseudoisochromatic color plate test, "Color Vision Testing Made Easy" (CVTMET) has recently been introduced. Said to be designed for all age groups, including pre-school children, it uses the identification of simple shapes and objects to detect red-green color deficiencies. We evaluated the CVTMET to determine if the test is suitable for color vision screening of young children. METHODS: Forty-one adults predetermined to be color normal (n = 20) or to have hereditary red-green color deficiency (n = 21), served as subjects. A battery of color vision tests including the Ishihara, Panel D-15, and the anomaloscope were used for diagnosis and color deficiency classification. Subjects were then tested with Part I and Part II of the CVTMET test and results were compared to the Ishihara, Panel D-15, and anomaloscope. In addition, the CVTMET was used to screen for color vision deficiency in 152 kindergarten children 5 to 7 years of age. RESULTS: The pass/fail results for the adult subjects were the same for Parts I and II and compared favorably with the anomaloscope. There were no false positives (100% specificity) and only a few (2 of 21) false negatives (90.5% sensitivity). The two color-deficient subjects who passed the CVTMET had the mildest color deficiencies (simple deuteranomaly) and also passed the Ishihara test. Testability of kindergarten children was found to be 100%. Color vision deficiency occurred in 5.06% of the boys, which is about the same frequency found in older boys of similar ethnic background. CONCLUSION: This preliminary study indicates that the CVTMET appears to be an excellent screening instrument for red-green color deficiency in adults and has been shown to be useful for examining color vision in children 5 to 7 years of age.

Adult↗
PubMed2003

Fixed green and brown color morphs and a novel color-changing morph of the Pacific tree frog Hyla regilla.

Pacific tree frogs Hyla regilla are typically either green or brown in dorsal coloration. The frequency of green and brown individuals is known to fluctuate seasonally. Previous investigators have generally assumed that the green and brown body colors represent a "fixed" polymorphism and that seasonal changes in the proportion of the two body colors are a consequence of differential survival of the two color morphs. Here we report that, in addition to the "fixed" (i.e., non-color-changing) green and brown morphs of H. regilla, there are some individuals that can change hue between green and brown. The distribution of color-change ability in our study population is bimodal, suggesting that "color changers" are a distinct morph rather than one extreme of a continuous distribution of color-change ability. Our findings suggest that background brightness, not hue, triggers color change in the newly discovered morph and that this change requires days to weeks to occur. Such slow color change is not well suited for making short-term changes in color as a frog moves between differently colored substrates. Rather, seasonal changes in habitat characteristics and/or microhabitat use are likely to maintain color-change ability. Color polymorphism and color-change ability appear to represent alternative responses to divergent selection for crypsis in a heterogeneous, seasonally variable environment.

Animals↗
PubMed2003

Color realism and color science.

The target article is an attempt to make some progress on the problem of color realism. Are objects colored? And what is the nature of the color properties? We defend the view that physical objects (for instance, tomatoes, radishes, and rubies) are colored, and that colors are physical properties, specifically, types of reflectance. This is probably a minority opinion, at least among color scientists. Textbooks frequently claim that physical objects are not colored, and that the colors are "subjective" or "in the mind." The article has two other purposes: First, to introduce an interdisciplinary audience to some distinctively philosophical tools that are useful in tackling the problem of color realism and, second, to clarify the various positions and central arguments in the debate. The first part explains the problem of color realism and makes some useful distinctions. These distinctions are then used to expose various confusions that often prevent people from seeing that the issues are genuine and difficult, and that the problem of color realism ought to be of interest to anyone working in the field of color science. The second part explains the various leading answers to the problem of color realism, and (briefly) argues that all views other than our own have serious difficulties or are unmotivated. The third part explains and motivates our own view, that colors are types of reflectances and defends it against objections made in the recent literature that are often taken as fatal.

Animals↗
PubMed1996

Limitations of surface-color and apparent-color constancy.

Color-constancy mechanisms have been studied and discussed in a number of investigations. However, there has been little attempt to reveal how color constancy deteriorates as the conditions for it become less than optimal. We carried out a series of asymmetric color-matching experiments, using two criteria: surface-color match and apparent-color match. With brief adaptation the degree of color constancy increased as chromatic cues were added in the surround. In the condition of black surround, the test stimuli appeared self-luminous, and chromaticities of the chosen matching stimuli were the same as the physical chromaticities of the test stimulus, indicating a total deficiency of color constancy. With 15 min of preadaptation to the illuminant, the surface-color matches showed almost perfect color constancy under illuminant change. In both adaptation conditions, the chromatic-shift of matches from what would be expected for perfect color constancy increased gradually between 1,700- and 30,000-K illuminant, as chromaticity of the illuminant departed from 6,500-K illuminant. Under 1,000-K illuminant the surface-color appearance became totally achromatic, and color constancy was completely lost. Our results show that, even with brief adaptation to the illuminant, the contribution of the surrounding stimulus is large enough to achieve a fair degree of color constancy, but complete adaptation to the illuminant helps to achieve almost perfect color constancy.

Adaptation, Physiological↗
PubMed1996

Color memory and color constancy.

Color constancy is the perceived stability of the color of objects despite changes in the light illuminating them. An object's color is considered constant if the current perceived color is judged to be in accord with the remembered one. Thus the accuracy and precision of color memory are fundamental to understanding this classic problem. Two hypotheses of color memory are tested here: (1) the photoreceptor hypothesis, which states that the color recalled from memory reproduces the light absorbed by each type of cone and (2) the surface-reflectance hypothesis, which states that the color recalled from memory is based on an inferred spectral reflectance of a surface that does not depend on the spectral distribution of the illuminant. In the experiments a test color is surrounded by either (i) a complex pattern composed of several colored patches or (ii) a uniform "gray" field at the chromaticity of the illuminant. In a control condition the test color is presented on a dark background. Long-term memory of the test color is measured in a production task begun 10 min after the end of the learning phase. In general, the results with a complex surround are consistent with the surface-reflectance hypothesis but not with the photoreceptor hypothesis. Color memory with the "gray" surround, on the other hand, shows a much stronger effect of the illuminant used during learning. These results are consistent with computational models of color constancy that require three or more chromaticities in view.

Color↗
PubMedDate not supplied

[Color categorization and the structure of perceptive color].

This paper is an attempt to develop a coherent framework for understanding, simulating, and predicting color categories. The process of color categorization can be understood as a structuring of preceding color experience on the basis of statistical distribution of light in observers environment. A proposed computational model of color categorization includes: 1) distribution of R, G, B pixel values representing a sample of 630 color images of natural scenes (analogue of physical light experience); 2) transformation of the R, G, B pixel values into L*u*v* coordinates of the CIELUV color space (analogue of the process of color perception); 3) distribution of the L*u*v* coordinates representing the sample of the color images (analogue of perceived color experience); 4) k-means clustering algorithm of the L*u*v* coordinates representing the sample of the color images (analogue of the process of color categorization); 5) location and order of color clusters (analogue of location and order of color categories). The proposed computational model enables us to predict the location and order of color categories, being consistent with psycholinguistic data.

Algorithms↗
PubMed2006

Comparison of antifungal activity of white-colored and gray-colored mineral trioxide aggregate (MTA) at similar concentrations against Candida albicans.

The killing effect of similar concentrations of white-colored MTA and gray-colored MTA against Candida albicans was assessed in vitro using the tube dilution test. A direct correlation was found between MTA concentration and its killing effect on C. albicans. At time period zero, both white-colored and gray-colored MTA samples showed Candida growth regardless of the concentration. Tubes containing gray-colored MTA in concentrations of 50, 25, 12.5, 6.25, and 3.125 mg/ml and tubes containing white-colored MTA in concentrations of 50 and 25 mg/ml did not show C. albicans growth at any of the other time periods tested. Tubes containing white-colored MTA in concentrations of 12.5 mg/ml or less showed Candida growth at all the time periods tested. Statistically, a significant difference was found between tubes containing either 50 mg/ml or 25 mg/ml and tubes containing lower concentrations of white-colored MTA (p < 0.001). A significant difference was also found between tubes containing gray-colored MTA in concentrations of 12.5 mg/ml or less and tubes containing similar concentrations of white-colored MTA (p < 0.001). It appears that both gray-colored and white-colored MTA in concentrations of 50 mg/ml and 25 mg/ml are effective in killing C. albicans for periods of up to 1 wk. Lower concentrations of gray-colored MTA may still be effective while lower concentrations of white-colored MTA may not.

Aluminum Compounds↗
PubMed2000

Color from shape from color: a simple formalism with known light sources

Photometric stereo is a well-known technique for recovering surface normals of a surface but requires three or more images of a surface taken under illumination from different directions. At best, one may dispense with the need for multiple images by using colored lights tuned to camera filters. But a less restrictive paradigm is available that uses the orientation-from-color approach, wherein multiple broadband illuminants impinge on a surface simultaneously. In that method, colors for a Lambertian surface lie on an ellipsoid in color space. The method has been applied mainly to single-color objects, with ellipsoid quadratic-form parameters determined from a large number of pixels. However, recently Petrov and Antonova [Color Res. Appl. 21, 97 (1996)] developed an entirely local approach, useful also for multicolored objects with color uniform in each patch. We investigate to what extent a method such as that of Petrov and Antonova can be applied in the ostensibly simpler situation in which the complex lighting environment is known, i.e., a color photometric stereo situation, with all lights in play at once with only a single image to analyze. We find that, assuming a simple model of color formation, we are able to recover the object colors along with surface normals, using only a single image. Because we immerse the object in a known lighting environment, we show that only half of the equations utilized by Petrov and Antonova are actually needed, making the method more stable. Nevertheless, solutions do not exist at every pixel; instead we may determine a best estimate of patch color, using a robust estimator, and then apply that estimate throughout a patch. Results are shown to be quite good compared with ground truth. The simple color model can often be made to hold more exactly by transforming the color space into one corresponding to spectrally sharpened sensors, which are a matrix transform away from the actual camera sensors. In our study the reliability and accuracy of the normal vector and of the surface color recovery algorithm are improved by this straightforward transformation.

Journal Article↗