Measurement of color defective and normal color vision subjects´ color and luminance contrast threshold functions on CRT

To perform a more complete diagnosis on the effect of color vision deficiency on visual performance we measured luminance and color contrast threshold functions. Measurements were carried out on CRT for a range of spatial frequencies on color deficient and normal color vision individuals. Luminance and color contrast threshold is a measure of the recognition limits of low luminance and color contrast patterns. Both of them are function of the image features and spatial frequency. In our test patterns of stripes with a sinusoidal luminance profile were displayed on the monitor. The subject’s task was to detect the presence and orientation of these gratings. In the study 6 normal and 6 anomalous trichromats were measured. In the case of color contrast threshold measurement it is essential to apply colors with identical luminance sensation, otherwise the test person might be able to differentiate between the presented colors not based on hue but based on luminance. The increasing accessibility of computers and color monitors provides a platform for color vision tests based on brightness sensation correction. In our experiment we define the subject’s relative luminance sensation stimulated by the primary colors of the monitor with the method of direct heterochromatic photometry. Although, there were no significant differences in luminance contrast threshold between normal color vision and color deficient subjects, we found significant reduction in red-green color contrast threshold at all color defectives. The results prove the assumption that color deficiency has a negative effect on noticing details in color environment.