How'd he do that?

When I went to get a passport picture for my trip to South Africa, I noticed that the two passport photos weren't exactly identical - they were taken from slightly different angles. The passport camera had two lenses, spaced a little ways apart, projecting very slightly different images sidebyside onto the same film.

Since the way the brain perceives depth is by comparing the two slightlydifferent pictures it gets from the two eyes, similarly spaced a little ways apart, it occured to me that I could use two passport pictures as a stereoscopic (3D) image.

(Thanks to the folks at tummy.com who wrote and sell the XVscan extension to xv, which I used to scan in the picture.)

How do you see the effect?

To see the 3D effect, you either look at the crosseyed version and cross your eyes until the two images fuse, or look at the walleyed version and defocus your eyes (as if you were looking at something far in the distance) until the two images fuse. Some people have an easier time with one technique than the other. (Myself, I can only see these kinds of things crosseyed.)

Jay Sekora <js@aq.org>
last modified 1999.10.31