Well, the other day I was scanning the logs of what people had accessed off my site, and found that someone had apparently found my website while looking Thad Walker's paper Holography without Photography. Walker wrote on how you could write a simple C program (a dubious example was included in the paper) and use it to compute an image which you could then print on a laser printer, and then when you shine a laser through it (in a specific way involving a lens or two, but nothing too fancy), you can get the original image out.
Well, actually two copies of the image, one reversed from the other. And a bright red spot in the middle.
In the post above, I said I should do it sometime.
So I did.
And here it is. You might not be able to tell, but the icon I was trying for was a brain. It actually looks better in real life than it does here, but the resolution is limited to about 60x60 pixels, so I probably should have tried a simpler image. Still, I was kind of pleased with the result, as useless as it is.
When I get the system all worked out and understand the math more, I'll post a more elaborate HOWTO. Till then, try absorbing Walker's paper.
Today is Worldwide Pinhole Photography Day: a day where a simple hole and the wave nature of light conspire to create art. I was meaning to construct a simple pinhole camera, but didn't quite get around to it, and today might be too late, but if you are interested, try checking out the forums on f295.org for some awesome information.
I'm killing some time today thinking about how to compute optimal pinhole sizes for specific focal lengths, which leads rather naturally into the possibility of computing zone plates for as well. Note: there are no shortage of formula, none of which really agree, to compute optimal pinhole size, I want to derive them from principle. I'll let you know what I find out.
Above is my sole noteworthy pinhole photograph, taken from a simple cylindrical camera (hence the slightly wacky distortion) onto some kind of Ilford photographic paper, scanned, and inverted in Photoshop. I'll try to put up a picture of the camera later.
Addendum2: Here is the Flickr stream for pinhole photographs.