Abstract
For general use, lighting should not distort the color appearance of familiar objects. However, in special cases color distortion may be desirable. It is well-known that some spectral power distributions can increase the apparent chroma of objects, generally along a selected axis in color space, and always with a consequent distortion of hue. It is interesting to consider whether some individual observers could benefit from spectral tuning of this type. In particular, there is considerable interest in filters worn as glasses (such as those under the trade name EnChroma), which increase the contrasts of LvsM-cone color differences for individuals with diminished LvsM sensitivity. Instead of filtering the light just before it enters the eye, logically the same effect can be achieved by filtering the light source, or equivalently, by selecting an approximately equivalent combination of narrow-band LEDs. We have compared calculated color shifts produced by 3-primary narrowband LED sources to those for EnChroma-filtered broadband light, by simulating the cone-opponent responses of color deficient and trichromatic observers. We notionally illuminated the spectral reflectance factors of Munsell surfaces that were selected to yield a uniform circle of 36 hues in a cone-opponent space under equal energy white for a standard trichromatic observer. Chromatic contrasts were determined for the LED sources and the filtered broadband light, both for normal trichromats and observers who were deuteranomalous or protanomalous. For all observer types, we found qualitatively similar patterns of contrast enhancements for the two sources, confirming that narrowband LED luminaires may be a viable approach for enhancing color contrast for anomalous trichromats. However, in previous work we also found that color-normal observers adapt to the higher chromatic contrasts generated by wide-gamut LED sources (Takahashi et al. JOV 2019). Thus, the consequences of these adaptation effects should also be evaluated for color-deficient observers.