A revision of the CIECAM97s model

Abstract

The CIECAM97s model was adopted by the CIE in 1997 for colour imaging applications. It includes forward and reverse modes. Some problems in using this model were found in recent field trials. This article suggests revision to the model in two respects: (a) to make the lightness (J) zero when the Y tristimulus value is zero, under all surround conditions; (b) to modify the chromatic induction factor (Nc) from 1.10 to 0.95 for the dim surround condition. To avoid confusion, it is suggested that the revised version of the model be designated CAM97s2. The article also describes an alternative mode to achieve a more nearly exact reversibility between the forward and reverse modes.

Colour appearance of room colours

“…Colour appearance models1, 2 have been extensively applied to cross‐media colour reproduction across different imaging media under difference viewing conditions because its colour appearance attributes, such as, lightness, colourfulness, and hue are independent of various viewing conditions. In order to predict accurately the colour appearance of colours under a wide range of viewing conditions, CIE TC8‐01 recommended the use of CIECAM02 colour appearance model,3 which is based on CIECAM97s4 and incorporates a number of new revisions and simplifications 5, 6…”

Chromatic adaptation and colour constancy

“…The CMCCAT97 formula includes a power factor applied to the blue channel. It can only be solved iteratively in the reverse mode of the transform (Li et al , 2000). The CMCCAT2000 formula removes this problem by simplifying its structure.…”

CIE Color Appearance Models and Associated Color Spaces

“…This causes uncertainty in reversibility and complexity in the reverse mode. Li et al 26 addressed this problem and provided a solution by including an iterative approximation using the Newton method. However, this is unsatisfactory in imaging applications where the calculations need to be repeated for each pixel.…”

“…2. To correct the error that the lightness ( J ) was not equal to zero for a stimulus having a Y tristimulus value of zero, as reported by Li et al 26 .…”