Colorimetry and Dichromatic Vision

Abstract

Normal trichromats have three types of cone photoreceptors: L, M, and S cones (most sensitive to long, medium, or short wavelengths, respectively). Therefore, standard colorimetry is based on three variables (X, Y, Z). Dichromats only have two types of functional cones due to genetic factors. The main consequences are that dichromats (1) confuse colors that can only be discriminated by the response of the type of cone they lack and (2) make errors when naming colors. Chromaticity diagrams can be used to specify dichromats' color confusions. Confusion points represent imaginary stimuli that only activate L, M, or S cones. Confusion lines radiate from confusion points and represent pseudoisochromatic stimuli (i.e., colors confused by the corresponding type of dichromat if presented at an appropriate intensity). Dichromat's color appearance models have been developed to simulate the colors supposedly seen by dichromats, and there exist color simulation tools that implement some of those models.

“Red-Green” or “Brown-Green” Dichromats? The Accuracy of Dichromat Basic Color Terms Metacognition Supports Denomination Change

“…A superficial analysis of these results could wrongly lead one to conclude that they are only compatible with the LRH ( Roberson et al, 2000 ; Davidoff, 2015 ), in the sense that the internal color space is a “tabula rasa” where the linguistic-cultural factors freely segment the space into parts corresponding to each BCC (named with a specific BCT). Following this reasoning, the differences between the color experiences of normal and dichromatic vision (see, Moreira et al, 2018 ) do not pose a problem in this interpretation, but forms part of the evidence suggesting that universal factors are not necessary to explain the origin and development of BCTs.…”

A Novel Approach to Image Recoloring for Color Vision Deficiency

“… The second contribution assumes that the adaptation of confusing colors should be driven by a confusion-line based approach. Confusion lines are the product of extensive experimentations [ 3 , 6 , 9 ]. As such, they accurately reflect the way a dichromat perceives colors.…”

“…The impact of CVD on human vision is reflected on various physiological levels such as color discrimination, object recognition, color appearance, color naming, etc. [ 1 , 6 ].…”

“…A confusion line is defined as the locus of the set of colors confused by the protanope or deuteranope. All confusion lines intersect at a point outside the chromaticity diagram, which is called copunctal point and it is imaginary stimulus realized as the locus of the missing primary [ 3 , 6 ]. The color-blind confuses all colors belonging to the same line and therefore the entire line appears achromatic to him [ 4 ].…”

“…The color-blind confuses all colors belonging to the same line and therefore the entire line appears achromatic to him [ 4 ]. In essence, those colors are perceived by the color-blind with the same colorfulness, which consists of hue and saturation, but they can be identical only under the appropriate intensity [ 6 , 7 , 8 ]. Figure 1 shows some confusion lines for protanopia and deuteranopia taken from Judd’s revised chromaticity diagram [ 3 , 9 ].…”