Minimal Motion Color Blind Test
Description
Color blind test based on relative luminance measurement with minimal motion technique. It takes about 1 minute. You should stop the rotation of the wheel, or just find where the direction of rotation reverses. It is only a demonstration of the method, because its sensitivity (according to our measurements) is not adequate. The wheel rotates to clockwise (or counterclockwise). Increase (or decrease) the slider until the rotation stops or begins to rotate backward and press the NEXT button. It should be repeated six times, with red, green, blue colors from below and above.
Method
Heterochromatic flicker fusion
Normally we think of flicker when light’s switching between on and off, here it is switching between two different colors (thus “heterochromatic”). When these colors do only differ in hue, not in brightness, the disk does not seem to flicker any more at some position of the slider. This condition is called “equiluminance”.
Minimum motion technique
Another way to find out if two colors are of equal luminance is the “minimum motion” technique, as cleverly developed by Stuart Anstis & Pat Cavanagh (1983). The wheel rotates when we’re off equiluminance either left or right, and comes to an unrestful standstill around equiluminance. The explanation of “minimum motion” is somewhat involved, and has to do with a (nearly) color blind motion system choosing the best luminance match from frame to frame.
Two superimposed gratings moving in opposite directions, with the contrast of one grating fixed (here at 8%) and the other varying. (middle rows) The observer's optokinetic response to the summed gratings, generally follows the direction of the grating that appears higher-contrast. When the contrasts are perceptually matched the observer perceives only flicker, and the motion of the fixed grating is "nulled". (bottom row) A relatively low contrast (here 8%) luminance-defined grating can null the motion of a high-contrast equi-bright colour grating.
