Archived posting to the Leica Users Group, 2005/11/05
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]The main thing is, our visual perception system is perfectioned for "movie mode", not "stills mode". Our retina can be cheatened very easy with optical tricks like that. I use a similar animation in my classes at the Lucerne Art school to explain how our eyes/retina/nerves/brain work. The retina has cells that can send color informations, and others can send brightness/darkness informations, and the brain puts it together to an image. There are millions of cells overlayered, but each cell has a certain delay time after it has send an information, until it's ready for the next one. If, for a certain time which can vary from a few seconds to a minute or longer, one cell gets the same color/brightness value to communicate, it starts to compensate it with sending the inverse value (complementary color) in this interval time (called the "afterimage"). To come back on this sample: It's an animation with 12 frames. On each of the frame, there is one pink dot missing, clockwise. Now, if your eyes follow the rotation movement, you see the "missing dot" turning round. That's what really happens. That's not an illusion. Now to the illusions: If you focus on the cross in the middle, you start to see a green dot where the the missing pink dot, or better said, the grey background, should be seen. Why? It's the complementary color afterimage mentioned above. Make a red dot on a white paper, look at it for 10 seconds, then look at a white surface, and you'll see what I mean (or better said a a cyan dot). Then, if you look longer at the cross, even the pink dots do disappear and you see only the green one rotating on a grey ground. Why this? That's because the pink (normal image) and green (afterimage) impressions are neutralizing theirself, making it grey like the background. Try it with other colors here: http://www.michaelbach.de/ot/col_lilacChaser/index.html Didier >http://www.patmedia.net/marklevinson/cool/cool_illusion.html >Thought this was very interesting. I'm always interested in learning more >about visual phenomena.