Benham's Top
Benham's top is one of many classic examples of subjective colors. If you
spin the black and white circular disk, you should be able to see faint colors in
the position of the arcs. You can change the saturation of the perceived colors
by adjusting the spinning speed with the scroll bar. Different sections of the arcs
produce different colors from red to blue. Reversing the spinning will reverse the
order of colors.
The following version was adapted in response to
Josef K Nagler's suggestions
Sequential color change based on Josef K Nagler's 1956 US Patent
(METHOD AND APPARATUS FOR PRODUCING COLOR):
The above panel has six identical groups each of which has three bars (hence 18
bars) - left, middle and right - corresponding to the inner, middle and outer sections
of the arcs of the above disk. You can cover any groups or bars, the remaining subjective
colors persist. You can use the speed control scroll bar to slow down the frame
rate to see the image sequences that produce the subjective colors. You can also
use the scroll bar to reverse the sequence and watch the subjective color pattern
reverses accordingly.
(Originally Developed in November 1999)