Color appearance model incorporating contrast adaptation - implications for individual differences in color vision

Daltonization or colour enhancement: potential uses and limitations [Invited]

The main perceptual-cognitive limitations of CDOs (Colour Deficient Observers) are analysed, along with the uses and limitations of tools that either transform images so that CNOs (Colour Normal Observers) see them as CDOs (simulation) or transform images so that CDOs can use them as CNOs (daltonization). The four main uses of colour (comparative, denotative, connotative, and aesthetic) are analysed, along with their relation to, alternatively, the ability to discriminate colour stimuli or to categorize colours. These uses of colour are applied to analyse the possible effects of daltonization tools.

Using Smooth Metamers to Estimate Color Appearance Metrics for Diverse Color-Normal Observers

Color-normal subjects sometimes disagree about metameric matches involving highly structured SPDs, because their cone fundamentals differ slightly, but non-negligibly. This has significant implications for the design of light sources and displays, so it should be estimated. We propose a broadly applicable estimation method based on a simple adaptive "front-end" interface that can be used with any selected standard color appearance model. The interface accepts, as input, any set of color matching functions for the individual subject (for example, these could be that person's cone response functions) and also the associated tristimulus values for the test stimulus and also for the reference stimulus (i.e. reference white). The interface converts this data into tristimulus values of the form used by the selected color appearance model (which could, for example, be X, Y, Z), while also carrying out the needed transform, which is based on an estimate of the subject's likely previous long-term adaptations to their unique cone fundamentals. The selected standard color appearance model then provides color appearance data that is an estimate of the color appearance of the test stimulus, for that individual subject. This information has the advantage of being interpretable within that model's well-known color space. The adaptive front end is based on the fact that, for any selected input SPD and the subject's unique color matching functions, there can be many different SPDs that are metameric for that individual. Since observer-to-observer color perception differences are minimized for spectrally smooth SPDs, smooth metamers predict color appearances reasonably accurately.