[Tig] contrast adaptation

Bob Friesenhahn bfriesen
Thu May 4 16:12:13 BST 2006

Thanks to oktobor for supporting the TIG
On Thu, 4 May 2006, glenn chan wrote:
> Though this visual quirk would be interesting:
> It seems like human vision adapts based on the level of contrast in a
> scene.  For example, if you've been wearing lab goggles for a while and take
> them off, suddenly the world will look like it has 'super high' contrast
> (super high being a technical term of course).
> A related/similar form of adaptation (and possibly the same???) is
> demonstrated at the following website:
> http://www.tutkie.tut.ac.jp/~mich/kitazaki.contour.html

This is very interesting and worth substantial consideration.  On a 
tiny CRT screen, most of the image will be in focus so there should be 
much less of this effect.  On large HDTVs, or on the cinema screen, 
the viewers eye will track objects on the screen based on current 
focus, whomever is doing the talking, or whatever catches the viewer's 
attention.  Sudden overall intensity changes will require a second or 
two for the eyes to adapt so the image can be properly seen.

It is clear that images on a screen which occupies only a small 
portion of the viewers field of view will be perceived much 
differently than the image on a screen which occupies a substantial 
portion of the viewers field of view.

This effect is a reason why it is often recommended that the screen be 
surrounded with illumination of appropriate color temperature and 
brightness rather than being completely black.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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