Short "hands on" documentation video of the interactive installation "Afterimage". In the project I used the effect of the afterimage and developed with Processing an application that helps you to generate an afterimage of yourself. Usually you see yourself only in mirrors and photographs, but by manipulating your eye it is possible that you see yourself for a short time anywhere you want. 
With the webcam of the computer I get the picture of the user. I reduced the details of the live picture so I got an image of the user that only consists of a few colored shapes. Finally I inverted the colors and added a countdown on which the user has to focus at for a few seconds. If he now looks on a white surface somewhere else he can see himself in colors.

The reason for this effect is the so called adaption of your eye. If the lighting conditions change we are still able to see really well. The pupils regulate how much light gets into the eye and the retina changes its sensitivity for light. The changes made by the pupils are fast, the change made by the retina takes some time, because it includes biochemical processes. 
Important for the understanding of the afterimage is the adaption the retina makes. Because there are 3 different receptors, the retina can not only adapt to light changes concerning light and dark, but also the color temperature. Because of chromatic adaption you get the right white balance for your vision. If the light situation has a stronger amount of red, the eye adapts and the receptor for red light gets less sensitive. In that way a surface still appears white although there is actually more red light. The same effect happens when you look longer on a turquoise surface. Your eye adapts to the light situation and the receptors for blue and green slowly get less sensitive. If you look now at a white surface, which sends light in all wavelengths to your eye the receptor for red is still the most sensitive. As long as the receptors need to adapt to the new light situation you will see the white surface in a red tone. 

Download "Afterimage" for Windows or Mac and get fascinated by the effect:


“Afterimage" was exhibited at the B-Seite 2015 in Mannheim. 

Music: Rumble -

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