| Calvin wrote: Quote:moviePig wrote: Yes, the red filter *does* block blue... and the blue, red (...except for the leakage inherent in all systems: red/blue, polaroid, or shutter-glasses). When you say that "what gets through" merely appears as dark, that is in fact the effect of its having been blocked. Since my last post I have realized that you are right about part of this and I was wrong. The red filter does indeed block out blue light, and it is the fact that none of it gets through that allows the image that was projected and reflected in blue to be perceived by the eye behind the red filter.... No... the red filter blocks that image made of blue light (as you've just realized), so that the eye behind the red filter can't see the blue image at all. (When your red-filtered eye looks at blue characters on your calendar, they turn black. The same thing happens to a projected blue image, i.e., it turns black... but, because you're in a darkened room, turning black is equivalent to vanishing. Meanwhile, for a blue line drawn on white paper viewed in a lighted room, the blue (again) does *not* pass the red-filter and thus appears black. But the surrounding white *does* pass the red filter. (Or, more specifically, the red portion of the all-color spectrum that white comprises passes it.) Thus, the blue line looks black on a white (although now tinted red) background. If, however, the line were drawn red, then it would pass the red filter just as the red fraction of the white background does. Thus, lline and background would look the same. Thus, the line would vanish (or, "wash out", as you would say). -- /---------------------------\ | YOUR taste at work... | | | | http://www.moviepig.com | \---------------------------/ |