Color imaging is such a ubiquitous capability in daily life that a general preference for color over black-and-white images is often simply assumed. However, tactical reconnaissance applications that involve visual detection and identification have historically relied on spatial information alone. In addition, realtime transmission over narrow communication channels often restricts the amount of image data, requiring tradeoffs in spectral vs. spatial content. For these reasons, an assessment of the discrimination differences between color and monochrome systems is of significant interest to optimize the visual detection and identification of objects of interest. We demonstrate the amount of visual image "utility" difference provided by color systems through a series of subjective experiments that pair spatially degraded color images with a reference monochrome sample. The quality comparisons show a performance improvement in intelligence value equivalent to that achieved from a spatial improvement of about a factor of two (approximately 1.0 NIIRS). Observers were also asked to perform specific detection tasks with both types of systems and their performance and confidence results were measured. On average, a 25 percent accuracy improvement and a 30 percent corresponding confidence improvement were measured for the color presentation vs. the same image presented in black-and-white (monochrome).
In many medical test designs, presence of a color spot can represent existence of a disease. This presence is usually verified by observation. For these tests, knowing the color discrimination threshold is necessary for modifying the indicator spots to have color differences above the threshold. In this work, a psychophysical experiment is used to determine the color difference threshold for a veterinarian test device from IDEXX company with blue-green spots. The study was conducted in two phases, In the first phase a preliminary investigation was conducted for the ideal situation, that is having perfect circular spots without any noise or non-uniformity. Method of constant stimuli was used to present designed test images to the observers. The results were analyzed using Probit analysis method. The second phase of the study was performed with objective of studying the effects of noise, imperfect spot shapes, presence of streak and presence of spot color gradient on the color difference threshold between the background and spot colors. The same experimental and analysis method was used in both phases. The results for the ideal situation showed an average discrimination threshold of 1.27 color difference (DE00) for overall data. For the realistic situation, the noisy appearance of the image and imperfectness of the shape of the spots did not affect the threshold when observers were expecting imperfect spots. However, the presence of streak and spot gradient increased the threshold.