The post by drlava in 445nM:
http://www.photonlexicon.com/forums/...al-capillaries
and the ensuing discussions reminded me of an optical illusion I stumbled into many years ago. I had a darkroom setup in a spare basement bathroom. One night I set off a camera flash in the complete darkness and noticed what appeared to be my image remaining in the mirror. I started experimenting with this and discovered that if the flash were held in the right position while I faced the mirror, I could indeed see a very clear image of myself for approx 10 seconds. I think this is what is referred to as afterimage, and I expect most of you are familiar with it. In my experimenting with it I discovered what turned out to be a really freaky party trick. The person doing it should begin moving their arms around while experiencing the afterimage. They realize they are moving while their perceived image is not. If the mood of the party is right and a few somewhat naive people are in attendance, you can really spook some people. One peculiar thing I noticed is that you have to keep your eyes still and staring straight into the mirror otherwise the afterimage immediately disappears. Fascinating.