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michaelrepucci 10-10-2008 11:25 AM

red/green anaglyphic ghosting
I'm using red/green anaglyphs, and getting a small amount of ghosting (i.e., I can see the left eye's red image through the right eye's green filter). I've been told that a good correction for this is to use a background that has some red and green in it (a dark brown), so that the contrast difference between the ghost image in either eye and the background is not perceptually noticeable. However, when I change the background color, the color of the objects changes as well, as if the red and green images are partially transparent. This negates the desired perceptual effect. Is there a way to prevent or work around this additive effect with anaglyphs to reduce ghosting?

Jeff 10-13-2008 10:52 AM

What type of background were you using before the dark brown? Generally a black or white background is used. When you use a black background you will see the red dots with the red filter and the green dots with the green filter. When you use a white background the green dots are seen with the red filter and the red with the green filter. Perhaps the effect of the ghosting is reduced more with one or the other.
Two major factors that contribute to ghosting are the spectral content of the light coming from each dot and the spectral filtering by each filter. Ideally, in terms of reducing ghosting, the spectral output of the primary colors will not overlap and the the filters will only allow light from the appropriate dot through. So, reducing ghosting means having a good combination of display and filters.

Here is a link to a paper that goes into the topic into some depth.

michaelrepucci 10-22-2008 10:26 AM

I would prefer to use a black background, but, to my knowledge, there is nothing I can do to adjust the spectral content of the display, nor the spectral filtering of the glasses. (Aside, of course, from buying a new display or glasses, which I don't want to do.) This is why I was content to perceptually remove the ghosting by changing the background color, but it doesn't behave as expected, and I'd like to know if I can change that behavior.

For example, imagine if I start a Vizard script without stereo, and I draw one red and one green square, not overlapping. When I then set the background color, the red and green squares do not change color. However, when I start a Vizard script with anaglyphic stereo, and draw a distant white square (so that the two images are non-overlapping), the color of the background DOES change the color of the red and green square. In the extreme case where the background is white, the red square becomes a pale blue and the green a pale yellow. Can I prevent this effect?

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