The McCollough Effect

Adapt to the colored images for a few minutes. That is, look at them continuously, but move your eyes around. Then look at the black and white image.

The effect isn't as strong as is should be. I don't know if this is a function of the glare of my monitor, or the colors I used, or what. If you have any ideas, please let me know.


Subject: McCollough Effect Demonstration
Date: Sun, 5 Mar 2000 21:15:16 -0800 (PST)
From: "Ryan E. Yount" <>

        I saw your example of the McCollough Effect on your web page. You
mentioned that the effect seemed weaker than it should be. You asked for 
any ideas, well here are a few: I think you may be right about monitor 
glare, in lab experiments it needs to be controlled due to the effect on 
perception of the gratings. Also, the colors you used seem a bit dull; 
that is, I think they could be a little brighter and would then provide a 
more intense effect. Bill Cheswick, at Bell labs, has a nice little web 
page with a pretty good demonstration, his colors are fairly bright and 
produce a better effect. His web address is:
One last thing I think may be affecting the intensity of the effect is 
the grating patterns themselves, in that the lines seem to be a little 
thick for the size patterns you are using. Try using thinner lines (make 
sure the black and color lines are the SAME size) and I think you may get 
a better result.
Hope that helps some!

Ryan E. Yount
University of San Francisco