Long ago, when he was working on the development of colour film, Land did an interesting experiment. He took two pictures of the same scene with B&W film, one through a green filter and one through red. The pictures were then projected on a screen from two different projectors: one with a green filter and one with a red filter over the lens. The result was a full colour image.
In 1963 I found a description of this experiment in Scientific American and did the experiment myself. Sure enough it worked. How and why? I don't remember the details, or the explanation, but it had much to do with the human eye and brain and less to do with the wavelength of the light involved. I'm going to try the same experiment, but instead of projectors I'm going to try to do something on my screen with Photoshop and layers. It may not be possible, but will give me something to mess with between now and when things get back to normal in a week or so. The most interesting thing about the whole experiment is that there were shades of blue in the images. I'm going to pick up some B&W film for my P30, before the shops shut, and have a go at this over the holidays. Don Dr E D F Williams http://personal.inet.fi/cool/don.williams Author's Web Site and Photo Gallery Updated: March 30, 2002
