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Haomiao Jiang, Joyce Farrell, Brian Wandell; A spectral estimation method for predicting between-eye color matches in unilateral dichromats. Journal of Vision 2015;15(12):20. doi: 10.1167/15.12.20.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction. There are several reports describing color vision in subjects who are dichromatic in one eye and trichromatic in the other. Between-eye color matches in these unilateral dichromats have been used to model color appearance for dichromats (Brettel et al, 1997 ). Methods. We describe a theoretical principle that makes specific predictions about the mapping from two cone class absorptions in the dichromat eye to three cone class absorptions in the trichromatic eye. Specifically, we propose that the brain estimates a spectral power distribution consistent with the two measured cone absorption rates; we use this estimate to predict the equivalent absorption rate for the missing cone type. We examined the implications of different spectral estimation methods, which is a severely under constrained estimation problem. These include (a) a smoothness constraint, (b) non-negativity constraint, and (c) natural scene priors. We implemented these calculations in open-source software. Results. Under some assumptions (smoothness only), a single linear transformation converts the dichromatic cone absorptions to the estimate for the missing cone class. This transformation matches some, but not all, of the color matches in unilateral dichromats. Adding additional assumptions (non-negativity) results in a nonlinear relationship between the two measured cone class absorptions and the estimated absorptions for the missing cone class. This observation predicts which wavelengths of light will appear the same to the dichromatic and trichromatic eyes (isochromes). The non-negativity constraint improves the agreement between predictions and measurements in unilateral dichromats (Alpern et al, 1983). Conclusion. Establishing a quantitative map from the two cone classes in a dichromat to a missing cone class has practical value for estimating color appearance matches between dichromats and trichromats (Brettel, et al.; Vischeck). In addition, we explain how the method can be useful for implementing a color difference metric for dichromatic observers.
Meeting abstract presented at VSS 2015
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