# Face change illusion: How does this work? **URL:** \ **Category:** Factual Questions\ **Created:** [May 17, 2007, 10:09pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517 "2007-05-17T22:09:42Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![noblebaron](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@noblebaron](https://boards.straightdope.com/u/noblebaron)\ **Post date:** [May 17, 2007, 10:09pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/1 "2007-05-17T22:09:42Z")
Would someone please explain how this works? It’s cool and freaky at the same time: [www.atwest.com/facechange](http://www.atwest.com/facechange) Thanks, -NB ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [May 17, 2007, 10:19pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/2 "2007-05-17T22:19:00Z")
You don’t have to go back 12 feet, just fuzz your focus a bit. Each face has two images, one clear and one blurry. When your eyes are focused you see the clear image preferentially. When your eyes are unfocused you see the blurry image preferentially. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [May 17, 2007, 10:19pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/3 "2007-05-17T22:19:37Z")
Full explanation, with examples, [here](http://cvcl.mit.edu/hybridimage.htm). Also check [here](http://www.newscientist.com/data/images/ns/cms/mg19325971.600/mg19325971.600-2_734.jpg) for a quick peek. ---
**Author:** ![cher3](https://avatars.discourse-cdn.com/v4/letter/c/da6949/32.png) [@cher3](https://boards.straightdope.com/u/cher3)\ **Post date:** [May 17, 2007, 10:19pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/4 "2007-05-17T22:19:44Z")
The best I can tell is that the features that distinguish the expressions when you are close are faint. When you back up they fade into the background, leaving the features that mark the switched expressions. For example, the ‘serene’ woman’s upper and lower lip lines disappears at a distance, as do her eyebrows. This leaves “brighter” areas visible that pick out the angry expression. When her eyebrows can’t be seen the highlight in that area makes it look like she is contracting her forehead. My office is too small to get far enough away to make the other one change completely, but I expect it’s the same process. ---
**Author:** ![Swallowed\_My\_Cellphone](https://avatars.discourse-cdn.com/v4/letter/s/9d8465/32.png) [@Swallowed\_My\_Cellphone](https://boards.straightdope.com/u/Swallowed_My_Cellphone)\ **Post date:** [May 17, 2007, 11:09pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/5 "2007-05-17T23:09:51Z")
It’s kind of fun if you open the images in Photoshop then use the filter “Gaussian Blur”. As you scroll up and down to increase or decrease the blur, you can see the transformation. ---
**Author:** ![SpoilerVirgin](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@SpoilerVirgin](https://boards.straightdope.com/u/SpoilerVirgin)\ **Post date:** [May 17, 2007, 11:28pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/6 "2007-05-17T23:28:03Z")
In this [recent thread](http://boards.straightdope.com/sdmb/showthread.php?t=419079), Dopers experiment with creating their own hybrid images. ---
**Author:** ![noblebaron](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@noblebaron](https://boards.straightdope.com/u/noblebaron)\ **Post date:** [May 18, 2007, 7:13pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/7 "2007-05-18T19:13:16Z")
Wow, thanks for the explanations and other cool examples of this phenomenon… it makes more sense now. Much appreciated, -NB ---
**Author:** ![Silk\_One](https://avatars.discourse-cdn.com/v4/letter/s/6de8d8/32.png) [@Silk\_One](https://boards.straightdope.com/u/Silk_One)\ **Post date:** [May 18, 2007, 7:26pm UTC](https://boards.straightdope.com/t/face-change-illusion-how-does-this-work/404517/8 "2007-05-18T19:26:03Z")
Here’s another cool one. [![](https://img.youtube.com/vi/QbKw0_v2clo/hqdefault.jpg "Charlie Chaplin Optic Illusion") ](https://www.youtube.com/watch?v=QbKw0_v2clo)