Dichromatic color perception in a two stage model: Testing for cone replacement and cone loss models

We formulate a two stage model of dichromatic color perception that consists of a first sensor layer with gain control followed by an opponent encoding transformation. We propose a method for estimating the unknown parameters in the model by utilizing pre-existing data from psychophysical experiments on unilateral dichromats. The model is validated using this existing data and by using predictions on known test images for detecting dichromacy. Using the model and analysis we evaluate the feasibility of cone loss and cone replacement hypotheses that have previously been proposed for modeling dichromatic color vision. Results indicate that the two stage model offers good agreement with test data. The cone loss and cone replacement models are shown to have fundamental limitations in matching psychophysical observations.