Color Contrast Sensitivity

An individual’s ability to differentiate two similar colors; The more sensitive an individual’s color contrast, the more colors they can see.

A test to determine Color Contrast Sensitivity presents you with a shape or letter comprising a background and foreground color. The test then moves the two colors closer together chromatically until the observer can no longer see the shape/letter because the colors are close enough that they appear identical – this moment represents the Color Contrast Threshold.

Usually, the two colors share a confusion line – either tritan or protan – meaning they would be impossible for a dichromat of that type – tritanope or protanope respectively – to differentiate. When the Color Contrast Threshold is determined in both the protan and tritan axes, the MacAdam Ellipse can be plotted on the Chromaticity Diagram.

A representation of the test is given below. The closer the colors are before the letter is unreadable, the better your color contrast sensitivity. In a real test, the letter changes every time a guess is made. Upon a correct guess, the colors move closer together. On an incorrect guess, they move further apart. Note: these colors have to be calibrated for each individual to be Isoluminant.