Making 3D Pictures
The Red / Cyan Method

Clive R. Haynes FRPS


What is a 3D image?
The human optical system views a scene and transmits messages to our brain which are the contents of two simultaneous, two-dimensional images, spaced about three inches apart. In making a 3D image we need to convince our optical system that, just as in real life, the two flat images presented add together to make a stereoscopic (3D) picture.

In Victorian times 'bioscope scenes' viewed with a hand-held stereo viewer were very popular. Two pictures were taken of a scene and pasted together side-by-side for viewing through simple lenses. They were very good with excellent depth and clarity.

Recently there's been resurgence in interest in 3D with cinema films and television adopting the technique.


How to do it.
The first requirement is to take two pictures of the scene, one left, one right. Obviously unless you are using a specialist stereo camera, it's best to avoid scenes with movement.

The viewpoint for pictures for most normal scenes, using say a 35mm to 100mm focal length lens (as per 35mm photography) needs to be about 3 inches apart - this is the average distance between the left eye and the right eye. Special devices can be bought to do this with extreme precision; however it can be done quite successfully by simply moving the camera. To do this take one picture (left) then lean to the right a little - go about 3 inches (75mm) keep everything level and without twisting the camera, take the second shot (right).

An improvement upon the simple 'move to the right' method can be made by 'toeing-in'. This is what you do.

When taking the left shot, look at the centre of the scene area for a 'reference object' and remember where it is within the frame.
After moving the 3 inches to the right, pan the camera back into the original scene area (this is 'toeing in').
Place the 'reference object' in the same spot as it was in the left image.
Take the shot.
The slight 'pan' almost re-aligns the image elements, however, they remain displaced by 3 inches to the right and this gives the stereo effect.
The 'toeing-in' is to reduce the amount of image area a that spills beyond the frame of each shot when combined in the 'anaglyph'. In this way a more complete image area is retained. Actually it's far easier and more obvious to do than explain!

Note: For wide-angle lenses you'll find that it's often preferable to reduce the L to R separation and ignore 'toeing-in' this is due to the exaggeration and distortion of perspective by wide-angle views. For longer focal length lenses L to R separation will need to be greater than 3 inches. Indeed for distant scenes with long telephoto lenses the separation may be several feet. However, with greater separation it's more difficult to maintain correct registration. You'll need to experiment.

The two resulting pictures can be viewed as a stereo pair. If they are slides, then a double viewer can be used to recreate the 3D scene.
If prints, then I find that placing two 5" x 7" prints (one 'left', one right') side by side about 3 feet away and deliberately going cross-eyed to view them works crudely. Some people find that going cross-eyed is not at all easy - so it's not something that I would recommend.

Work in RGB (colour) mode
Finally, I recommend using a colour image (either scanned or DI capture) as the image will be available for either colour or 3D stereo use. Also, for monochrome, the tone and contrast can be adjusted to suit the subject and aid spatial separation. If you're scanning-in remember to choose RGB. Any Greyscale images must be converted to RGB before beginning the process outlined below.

I hope this covers most eventualities.


An Anaglyph
A popular form of 3D picture is a two-colour image that recreates depth by making each half of the stereo pair a different colour; this is known as an 'anaglyph'. For many years red and green was the most common combination. However, now red and cyan more often preferred. Using red / cyan makes it easier to view colour images in 3D as more colour information is retained.

The accepted convention is to make the image for left eye image red and for the right eye, cyan.

Digital imaging has made the production of anaglyphs simple.

The word anaglyph incidentally, derives from the Greek - anaglyphos, anaglyptos - in low relief - ana, up/back, glyphein, to engrave or carve. 'Anaglypta' wallpaper has the same derivation!

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