[tig] This is very grey to me...

S. T. Nottingham nottinghams
Fri Apr 23 02:31:07 BST 2004


Jeff,

You can see a similar effect when a gray patch is surrounded by green, and a
second identical patch surrounded by magenta. Even though both patches are
the same, they look different because of their surroundings. The same is
true here. Patch A has much lighter surroundings that patch B. You must
always remember that the human brain is the most complicated and powerful
"color corrector" in the human experience. This is why both daylight and
tungsten look "white" to humans in day and night environments respectively.
But everyone of us should be aware of what happens when tungsten
illumination is photographed by daylight balanced film stock. You should
also be aware that staring at anything long enough will cause any dominate
color balance to become more neutral to the human brain. That is why
colorists should look away or leave the room periodically, and if it looks
the same when you return, you have made the correct call.

There is no way to "turn this off", and I doubt you would want to even if
you could. It would change the human experience entirely. Part of the art of
color correction is becoming aware of these type of psychological conditions
imposed upon us by the human brain. If it helps you cope with reality any
better, I doubt the effect shown would be any where near as dramatic when
viewed by the human eye directly instead by way of photograph. Hope this
helps your quandary.

Tom Nottingham
Retired Colorist

 -----Original Message-----
From: 	tig-admin at tig.colorist.org [mailto:tig-admin at tig.colorist.org]  On
Behalf Of jeffh
Sent:	Thursday, April 22, 2004 9:58 AM
To:	tig
Subject:	[tig] This is very grey to me...

thanks to Pat Howley of MTI for supporting the TIG.
--


http://www.ebaumsworld.com/checkershadow.html

Some of you may have seen this before, or other things
like it; I just found this yesterday.  Look at box A, and
then box B.  They look like they are different shades....
but in fact they are not - they are identical.  If you believe
me, proceed to paragraph 2.  If you do not believe me,
save the pic, and open it up in a paint program.  Select
and move a part of A into B, or vice-versa.  See?
Alternately, hold your color dropper tool over box A and
see what color is displayed (Jasc's Paint Sho Pro has
this; I am sure other programs do as well, tho I am not
sure if the "dropper" would be called something else).
See what RGB value is displayed; I get 107 107 107.
Then hold the tool over box B (try to keep away from the
edges) - the same 107 107 107, right?

So, my question is: why?  Why do both boxes appear
different when they are in fact the same?  What is making
my brain perceive the boxes as different - and better yet:
how do I get my brain to stop doing that!?!??  <cough>
It is not the prescence of the letters "A" and "B" - if I crop
each box, and paste both into a new image, they now look
the same, thus proving that the letters are not causing the
boxes to appear different in the original image. Nor is it the
prescence of the cylinder - removing it, or altering it's color
does not change anything.  Therefore, I am figuring it is not
the boxes themselves, but the SURROUNDING boxes - but
what gives?  Why would the shade of any of the surrounding
boxes affect how others are perceived?

And from that, comes two questions:

1.  If the board were oriented differently, would this affect how
the brain perceives the boxes?

2.  How about looking at the same box in real life as opposed
to on a computer screen - would that make any difference?

Anyone who can properly explain this will be owed a night of
heavy drinking....



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