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Name: Isabel Q.
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: 4/9/2003
Question:
Thank you for answering:

1) Why, when we spin a color wheel, do we see a whitish blur instead of individual colors?

2) Why do you need to spin color wheel fast in order to get whitish color. Does it relate to the speed of light?

Replies:
The major factor is by far not the speed of light. Rather, it is the response time of cones and rods in the eye. When a wavelength of light strikes the retinal, that "signal" decays in about 1/25 sec. The superposition of tri-color stimuli (typically yellow, cyan, and magenta) "excites" all of the rods and cones, giving the visual perception of white light (approximately). So the sectors of the color wheel must rotate quickly enough so that each color segment superimposes the other two in 1/25 of a second or less. The shading will change if the speed is increased or decreased slightly. For the distances involved, the speed of light is almost infinite.

Vince Calder


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