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From: phd@speech1.cs.cmu.edu (Paul Dietz)
Newsgroups: sci.electronics,comp.graphics
Subject: Re: Perceptual Color (was: Re: Looking for Blue LEDs)
Keywords: Fechner-Benham top...
Message-ID: <3357@pt.cs.cmu.edu>
Date: 20 Oct 88 11:28:37 GMT
References: <987@hydra.riacs.edu> <1692@eos.UUCP>
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In article <1692@eos.UUCP> jbm@eos.UUCP (Jeffrey Mulligan) writes:
>From article <987@hydra.riacs.edu>, by julian@riacs.edu (Julian E Gomez):
>> What you saw is known as a Fechner wheel.
> Is this another name for "Benham's top?"  This one is a disk
> half white and half black, with some black tangential arcs on the
> white half.  One point that is illustrated by this particular
> demonstration is that the (weak) hues evoked depend on the spatial
> context, not just to temporal pattern at the "colored" area.

Actually, some people refer to it as the Fechner-Benham Subjective
Color Phenomena. For you folks anxious to try programing this
on your favorite graphics machine 6 Hz is about the magic number
you need, and make the black strips very thin. I did this on a Mac
several years ago with good results. The hardest part is making
sure that you're synced with the vertical retrace. Contrary to
popular belief you do not need a moving edge! I used just three
frames: one all black, one with two thin black lines in the top
half, and the last with two thin black lines in the bottom half.

Paul H. Dietz                                        ____          ____
Dept. of Electrical and Computer Engineering        / oo \        <_<\\\
Carnegie Mellon University                        /|  \/  |\        \\ \\
--------------------------------------------     | | (  ) | |       | ||\\
"If God had meant for penguins to fly,             -->--<--        / / |\\\  /
he would have given them wings."            _________^__^_________/ / / \\\\-