Anaglyphs
[Note: Anaglyphs provide an alternative method to present two stereo views of an image to the left and right eye. This is done by encoding the views into a single image using different colors, and then viewing through complementary colored glasses (typically red/blue or red/green). This is commonly used in "3D comic books", but applies equally well to photographs. The following excellent discussion of these techniques was provided by David Hutchinson:]
There are LOTS of ways to make anaglyph photos. In simplest terms: The basic idea is to use the principle of complementary colors to encode your stereo information. A stereo photograph requires a left eye view and a right eye view; to view a photo in stereo the left eye must see ONLY the left eye view and the right eye must see only the RIGHT eye view. Any combination of two complementary colors can achieve this.
In practice... You can produce an anaglyph stereo photo using one of the following methods:
- By double exposing the film through complementary colored filters: click off one exposure through one filter for the first eye view, shift the camera over for the other point of view without advancing the film, change filters and expose for the other eye view. You must, of course, use color film.
- You can take left and right stereo negatives and print them one at a time through complementary filters onto color positive paper to get an anaglyph photo in the darkroom. This works best with black and white negatives, but color negatives can be used, too, it's just a little trickier getting a pleasing color balance in the middle of the spectrum.
- You could project left and right stereo positive slides (black and white is easiest, but color is not impossible) with complementary colored filters over the projection lens. The results tend to be muddy, but it does work with simple subjects.
- Use a Polaroid camera with double exposure capability; use color film. Take the left eye exposure through one filter, re-cock the shutter, change filters, shift the camera and exposure the other eye view. Presto! An instant stereo anaglyph print.
- Using a mirror box and beamsplitter rig, you can make anaglyph movies or stills by taping complementary colored gels over the left and right mirror openings. A company in England makes such a device for amateurs, who don't want to set up dual projection or who don't care to split the already tiny 8mm frame for left and right eye views.
Well, this could go on and on. Just apply the basic principle to whatever situation you are in and to what you have to work with.
FILTER CHOICE: Pretty broad range here, too. Many have already been suggested. Kodak's "Filters for Scientific and Technical Use" is the ideal reference with its very useful spectrophotometric graphs. Some people like to use the pair of Wratten #29 with #44; or you might try #24 with #60; maybe a 26 with 38A, or #25 with #55, etc. What you use depends upon the lighting (daylight or tungsten) and what kind of film you are using. You'll find yourself experimenting A LOT; so you may as well buy quite a few of the filters as gelatin squares from Kodak, and be prepared to play around.
Personally, I use a the #29 with a #44 to make anaglyph color slides. Basically, color slide film has red, green and blue sensitive layers (well that used to be the case, but now there are also lots of other layers added to improve color rendition). The red, green and blue layers are replaced with dyes that are cyan, magenta and yellow. Generally, if your filters achieve a good split between red on one side and green/blue on the other, the positive slide will have one eye view in cyan dye and the other eye view in magenta/yellow dye or red. If you juggle the amount of "crosstalk" between red and green, but stay away from blue, you can achieve a good yellow in the positive image, but this is really tricky.