Appearance match between hardcopy and softcopy using lightness rescaling with black point adaptation

摘要

When we view a softcopy image on a CRT display, typical CRT white point color temperature is 9300K and standard ambient light is 5000K. In this case, the black on the CRT screen is lightened and the chromaticity of the black is far from the achromatic axis because of the reflection of ambient light on the CRT displays. Also, when viewing hardcopy in the same environment as a CRT monitor, the chromaticity of the printer black is far from the achromatie axis. If such a printer were the source device and CRT monitor the destination device, dark printer colors canntot be reproduced on the destination device because, for dark colors, the gamut of the destination is smaller than the gamut of the source. Thus, lightness compensation is needed to reproduce dark colors on destination device. Three methods were considered: (1) Simple lightness compression method, (2) Complete black point adaptation method that consists of mapping to the CRT black, (3) Incomplete black point adaptation method that is a compromise between method (1) and (2). Visual experiments were performed to investigate these methods. The results indicated that the appropriate black point adaptation ratio is located between softcopy and hardcopy black points.