Docteur Christophe: Anaglyph, what a hell is that?

What is an anaglyph ?
I won’t explain it on a very technical way. Others already did and I am only a simple “amateur”.
We see the relief, and therefore the third dimension, because we have got two eyes seeing two different view of the same scene. So, our vision of the relief is stereoscopic. Cyclops, with their single eye, see a flat world whereas flies with their loads of eyes should see a very different relief of the World. Ask one of these about it next time you cross their way!

Left eye image Right eye image

Here is a graphical explanation of the phenomena. When looking at an object, for example that cube drawn below, both eyes see slightly different images.

Parallel stereoscopic pair (L-R)

We can get the perception of the relief, by placing the couple of images side-by-side (in one way or the other way round) and looking at then through an optical device witch allows one eye to see only one image. These images are called a stereoscopic pair. Some people are able to see the relief by squinting in a peculiar (crossed, parallel or even both dispositions). However it is quite an eye-training.

Crossed stereoscopic pair (R-L)

This time, left image is on the right side.

Left view through red filter Right view through cyan filter

Anaglyph is an alternative to the stereoscopic pair. The two images are superposed after passing through two different coloured filters. If the two colours used are complementary, the resulting picture keeps nearly the natural aspect and colours of the original scene (except the two filter’s colours). Conventionally, a red filter is used for the left eye and a cyan filter for the right one, but any other combination does works.

Mixing both = anaglyph

We are done!

Use red/cyan glasses with the red glass on the left side.

For more details, see Rafael Mullor’s website (Spanish) explaining the conversion of a stereoscopic pair to an anaglyph in a colorimetric point of view. See French stereoclub’s Website (French) for history of 3D shooting. That page (English) describes stereoscopic composition and shooting rules.
Note: If you look at anaglyphs for too long, everything will appear in 3D (even a flat blank sheet of paper) when removing the bicoloured glasses from your nose. It is scary but not dangerous. Colour vision comes back to normal after a while.

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Anaglyph, what a hell is that?

Left eye image Right eye image

Parallel stereoscopic pair (L-R)

Crossed stereoscopic pair (R-L)

Left view through red filter Right view through cyan filter

Mixing both = anaglyph