A Conversation for 3D Stereograms
Jerms - a Brief flicker and then gone again. Started conversation Jun 10, 2004
I did an essay on optical illusions many many years ago, and I remember discovering that for the sake of anaglyphs, any two different shades of yellow worked better than red and green. Red and green worked better than any other combination, though.
Any ideas why this might be? I never found out. Also do you have any idea why we still use red and green filters - the second-best choice? Just force of habit, do you think?
I'd be interested to hear your opinion.
Known-as-Kent Posted May 30, 2005
To view any combined 3d image, you need to see each of the two images in only one eye. With an anaglyph, it is done with color. The red filter makes the white paper look red, and the red ink is not visible. The green or blue ink reflects very little red light, so it appears dark. In the other eye, the green filter makes the white paper look green, and the green ink is not visible. The red ink reflects very little green light, so it appears dark. Each eye sees its own image, and the brain sees the difference as depth.
You can use blue or green ink with a blue or green filter, and the problem is that sometimes the filter makes the paper look too dark. Green is not as dark as a good pure blue, so it is easier to see the red ink image.
Jerms - a Brief flicker and then gone again. Posted May 30, 2005
That's very well put, but it doesn't answer my question.
I understand the physics behind anaglyphic stereoscopism, but I don't understand why we continue to use red and green filters, when yellow and other-yellow filters work better. Aparrantly.
Thanks for taking the effort to answer, though.
TellingBone Posted Jun 7, 2009
When you talk about 'shades' of yellow, do you mean a reddish yellow and a greenish yellow, or do you mean a dark yellow and a light yellow?
Destriarch Posted Jul 31, 2009
Modern anaglyphic stereo glasses don't actually use blue or green lenses at all, they use red and cyan. Cyan is a combination of blue and green. This means that you lose less colour information. A yellow/yellow split will tend to filter out a lot of the colour of an image, so that while the 3D effect may be enhanced, the entire scene will appear washed out and yellow. This is less a problem with red/cyan glasses since all three primary colours are represented. Sure one eye sees a red tinge and the other one a greeny-blue one, but the combination of looking through both at once cancels this out to some degree.
Additionally, when working on a computer one of the commonest ways of judging colour is to split it into Red, Green and Blue components. This means that all you need to do to create anaglyphic stereo on a computer is to have two pictures from slightly different positions (about four to six inches appart, facing the same way). You then strip the 'Red' channel out of the left image and the 'Green' and 'Blue' channels out of the right image. Combining these three channels together creates an anaglyphic stereo image. This is far, far simpler than messing around with shades of yellow.
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