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Toward the design of an optimal filter for enhancement of dichromat monocular chromatic discrimination.

Based on Farnsworth's theories of color confusion and discrimination, "rose-colored" or "pink" filters such as the X-Chrom material of 0.16 mm in thickness or the Kodak Wratten no. 30 filter act as monocular chromatic enhancers for red/green color deficients by virtue of colorimetrically lengthening color space in a direction perpendicular to the dichromatic axis of color confusion. Using derived formulas for dichromat colorimetry, a set of representative isoluminant-isochroma spectral hues, and interactive computer graphic colorimetric tools, it is possible to determine an optimum spectrophotometric filter curve. Such a filter has minimal middle wavelength transmission and is optimal in terms of providing maximal monocular chromatic clues for discriminative tasks involving confused colors.

Color Perception↗

Dichromatic confusion lines and color vision models.

An attempt has been made to explain how dichromatic confusion lines can be used in building a model for color vision. In the König color vision model the fundamental colors are located on the mixture diagram at the copunctal points for protanopes, deuteranopes, and tritanopes. In Fry's model the copunctal points fall on the alychne and cannot represent the fundamental colors. On a constant luminance diagram the confusion lines for the different dichromats are sets of parallel lines. This arrangement of the confusion lines can be explained in terms of a zone theory of color vision.

Color Perception↗

Analysis of the Mark II edition of The City University Colour Vision Test.

The City University (TCU) test was administered to 50 dichromats and 56 anomalous trichromats. Certain poorly performing plates are identified from the accuracy of diagnosis compared with the Nagel anomaloscope and the number of dichromats passing the plates. Some plates are indicated as providing a more reliable diagnosis, particularly when used in combination. The performance of the plates is compared with their colorimetric properties. The desaturated plates, which were not part of the Mark I test, are shown not to provide the intended extent diagnosis.

Color Perception↗

Color mixture data for normals and tritanopes.

In the author's theory of color vision the blue and the green fundamental fall on a tritanopic confusion line. This provides the basis for comparing the mixture data of a tritanope with those of a normal. At the red end of the spectrum the data conform very well to what is predicted by theory. At the blue end the data point to the possibility that the pigment responsible for the red response may differ from the pigment involved at the red end of the spectrum.

Color Perception↗

Identification of polarity in FM 100-Hue plots: a comparison of methods.

Several methods which have been proposed to aid the identification of polarity in Farnsworth-Munsell (FM) 100-Hue test plots are described. The assumptions which underlie one type of method are discussed and problems identified. Two methods are taken as representative of the two types of analysis and their performance compared on plots from congenital and acquired color defectives. The key difference between the two methods and the types of method which they represent lies in the imposition of symmetry on the plot. From the performance of 200 diabetic subjects, the problems created by the presence of monopolar plots, plots with unequal magnitudes of errors in the two poles of bipolar plots, and plots in which the two poles are not diametrically opposite are highlighted. It is concluded that the simpler type of analysis is sufficient and retains more information.

Color Perception↗

Stiles-Burch two-degree color mixture data.

The 2 degree color mixture data of Stiles and Burch have been analyzed to study the differences between individual subjects and the lack of precision at the blue end of the spectrum. The luminous efficiency data have been compared to those of Judd's 1951 observer and the 1931 standard observer. The mixture data have been compared to those of Wright and Guild and have been related to mixture data of dichromats. One of the ten observers was found to have a luminous efficiency curve similar to that of a protanope and was excluded from the average data.

Color↗

What do color vision defectives say about everyday tasks?

A lengthy questionnaire was administered to 102 people with defective color vision and to an equal number of people with normal color vision. The questionnaire asked about the subjects' awareness of their defect and their knowledge of defective color vision as well as exploring the difficulties they experience with color at work and in pursuing leisure activities. The questionnaire was administered in the consulting room under conditions that might be expected to elicit frank replies. Nearly 90% of dichromats and up to two-thirds of anomalous trichomats reported difficulties with everyday tasks that involve color, nearly one-half of the dichromats and one in five anomalous trichromats reported difficulty with traffic lights, and similar proportions reported color difficulties in their present jobs. Substantial numbers reported that their color vision defect had affected their choice of career and many had been excluded from a chosen occupation. The screening of color vision in schools and provision of appropriate career counselling is urged.

Activities of Daily Living↗

Scoring the Farnsworth-Munsell 100-hue for vocational guidance.

BACKGROUND: We considered whether the color discrimination of mild color defectives scoring < or = 100 is the same as that of normals. METHODS: We analyzed the FM 100-hue results of 126 normals and 94 congenital color defectives retrospectively by considering the Total Error Score (TES) and individual cap errors (error profiles). RESULTS: A TES of 100 passes 95% of normals and 24% of congenital color defectives. The error profiles of some of the mild defectives who pass show abnormal peaks along a red-green axis. An error > or = 5 in these regions is a good indicator of abnormal color discrimination. CONCLUSIONS: Some 30% of mild defectives (TES < or = 100) have limited hue discrimination in the red-green domain, so both the TES and error profiles need to be considered when providing vocational guidance.

Adult↗