scope:

This document provides a colour appearance model which is applicable for colour management systems, used in the imaging industries, that involve related colours. The main applications of the model are the evaluation of photographic prints (which requires a light source for viewing) and self-luminous displays, where the colours will be perceived as related colours. Background information is provided with respect to basic terminology and the evolution of the model, but it is assumed that the reader is familiar with the basics of colour science (Hunt and Pointer, 2011; Berns, 2019) and colour management (Green, 2010). For additional information regarding the complexities of gamut mapping and colour encoding, interested readers should refer to CIE publication 156:2004 (CIE, 2004b).

There are a number of possible applications for this model, and it is informative to provide a partial list of potential uses. Gamut visualization is a critical aspect in the evaluation of the colour capabilities of a given imaging device, medium or process. CIECAM16 can be useful for the comparison of device gamuts based on a set of perceptual attribute correlates. It is also possible to use CIECAM16 to provide a colour space for gamut mapping. Use of CIECAM16 does not define the domain, range or methodology for the mapping but it does provide perceptual attribute correlates to aid the understanding of the process. As with CIELAB, it is also possible to use CIECAM16 for interpolation, quantization, compression and other image based applications. Use of CIECAM16 for these applications, however, will require a full understanding of the processing requirements, such as the processing speed, memory requirements, etc. CIECAM16 has been shown to be as good as CIECAM02 (Li et al., 2017) in terms of processing speed, and at the same time it overcomes the problems that have been shown to exist with CIECAM02 (Brill, 2006; Gill, 2008).

It should be noted that the original colour appearance m odel, CIECAM02, and the new model, CIECAM16, have not been shown to be applicable to the colour appearance of unrelated colours, for example light sources seen in isolation. CIECAM02 and CIECAM16 are also only applicable to photopic levels where the eye is adapted to an average luminance greater than 5 cd·m⁻². CIE TC 1-96 is currently working on the extension of this range down to mesopic and scotopic levels.¹

¹ The work of TC 1-96 "A Comprehensive Model of Colour Vision" is still in progress. Please check the CIE website regularly for updates regarding the publication of this TC.