Re: an optical illusion?

[Stefan Jeglinski <jeglin@4PI.COM>]

> Riding home from a wedding today I was looking at the list of songs on the
> Santana 'Supernatural' CD.  The titles are written in many different colors.
> What struck me was that they appeared VERY 3-D, with reddish letters
> standing out and blue being pushed into the background--except that one
> title (The Calling--if you have the CD) had the red letters on dark
> background stand out while the red letters on blue background were pushed
> back.
>
> OK, my 'experimental observations'.  The number one feature was that I only
> observe the 3D behavior when looking through my glasses (blended bifocals)
> but I can hold the case away and look with the distance part or closer and
> use the reading part and maintain the 3-D look.  The phenomenon does require
> both eyes (not surprising) but does not require the plastic case of the CD.
> It seems to require pretty good illumination, but both sunlight and
> fluorescent light work.
>
> Anybody want to explain?  My main concern is whether the phenomenon somehow
> is related to a 'fault' in my glasses.  Can anyone with this CD and glasses
> see the same behavior.

I've seen this behavior for a long time, without any glasses at all.
I've always wondered about it, but never been able to come up with a
satisfactory explanation. My only other observation is that it seems
most stark with dark red and dark blue, two colors which appear more
or less at the 2 ends of human visual perception (IOW, could it in
any way be related to chromatic aberration in the eye?).

For those inclined to experiment with this, it is very easy to see
the effect on a web page (red letters against blue background, for
example). Very easy to change the colors for experiment: change an
html tag and reload the page. Possibly an excellent science project -
with a good 5-color inkjet printer, one can make prints to display
without a CRT or LED display.


Stefan Jeglinski