Orthogonal relations and color constancy in dichromatic colorblindness

Area of Science:

• Vision Science
• Colorimetry
• Genetics

Background:

• Dichromacy, a form of color vision deficiency, affects individuals with one non-functional cone type.
• Existing models often simplify dichromacy as a reduction of trichromacy, but complex genetic variations exist.
• Understanding dichromacy is crucial for accurate color perception research and applications.

Purpose of the Study:

• To analyze the spatial relationships within dichromacy using CIELUV uniform color space.
• To investigate the principles governing the color appearance space for different types of dichromacy.
• To compare the spatial structure of dichromacy with normal trichromatic vision.

Main Methods:

• Analysis of previously published dichromacy data.
• Plotting and analysis in CIELUV uniform color space to determine hue angles and spatial relations.
• Examination of color appearance under different illuminants (D65, D50, B).

Main Results:

• Identified four key principles in the spatial structure of dichromacy: complementarity, orthogonality of confusion and residual hues, orthogonality between protanopic and tritanopic systems, and inverse hue relationships.
• Protanopic residual hues were found to be more greenish-yellow and reddish-blue than traditionally described.
• Demonstrated that two dichromatic systems differ significantly from components of normal trichromatic vision.
• Chromatic adaptation in dichromacy correlates with that in trichromatic vision.

Conclusions:

• The spatial structure of dichromacy is complex and follows specific principles not fully captured by simple reductionist models.
• Certain dichromatic systems are fundamentally different from normal trichromatic vision.
• The findings clarify inter- and intra-type relationships in dichromacy and inform color science.
• Results have implications for color spaces like Munsell and CIELAB.