[visionlist] [cvnet] Color assimilation with faces - there's an App for that

[Larry Snyder]

Curious: how does color assimilation interact with simultaneous contrast? 
If I compare dark red stripes with light red stripes, the color 
assimilation effect means that the object behind dark red stripes should 
appear a darker red than the same object behind the light red stripes. But 
simultaneous contrast would have the reverse effect: the object should 
appear lighter when behind (and therefore in some sense framed by) dark 
stripes, compared to the same object behind light stripes.

What determines the net effect? Something about the relative spatial 
scales of the "object" patches compared to the "framing" stripes?

Surely these are non-linear effects, which suggests that with the right 
experiment one could figure out which effect occurs first - or are they
truly computed simultaneously?

Other similar questions come to mind ...

l

(Hi Karl!)





On Fri, 10 Jul 2026, Karl Gegenfurtner via cvnet wrote:

> Dear all,
>
> Some of you might have seen the demo Doris Braun and I gave
> at VSS demo night 2024, and at ECVP 2025 illusion night. 
>
> We took a portrait photo and overlaid thin stripes that made the
> face appear in the color of the stripes. The Munker illusion
> with faces. Back then that involved a lot of fiddling with Matlab,
> but now the whole process is available as a simple app that can
> be downloaded from the App store.
>
> You can create your own Munkerized face in seconds!
> And of course it is free.
>
> Here’s a link to a short description:
> https://www.allpsych.uni-giessen.de/karl/ColorAssim/
> and here’s the link to the App store:
> https://apps.apple.com/app/id6779916942
>
> It will be available on Google Play for Android in a week or two:
> https://play.google.com/store/apps/details?id=com.gegenfurtner.colorassim
>
> Enjoy!
>
> Best wishes,
>
> Karl
> --
> Prof. Karl Gegenfurtner, Abteilung Allgemeine Psychologie
> Justus-Liebig-Universität, Alter Steinbacher Weg 38, 35394 Giessen
> phone:  +49 641 9926100   mailto:gegenfurtner at uni-giessen.de
> fax:    +49 641 9926119   http://www.allpsych.uni-giessen.de/karl
>
>
>
>
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-- 
Larry Snyder                                  larry at eye-hand.wustl.edu
Professor of Neurobiology                       www.eye-hand.wustl.edu
Washington University, School of Medicine      Office:  (314) 747-3530
Dept of Neuroscience,  Box 8108                Lab:     (314) 747-4095
660 S Euclid Ave, St. Louis, MO 63110          Fax:     (314) 747-4370