Thank you again, Mr. Bill! Permitting a percentage of the light which the filter is designed to block, to pass through anyways, allows for the combinatory effects gained my using multiple filters.So, for your question about blocking magenta and yellow: to block magenta, as you now know, actually means to block both red and blue, while passing the third color, green. in a similar manner, to block yellow means to block both red and green, while passing blue. Clearly these two things are at odds with each other; the one passes only green, while the other passes only blue. If you combine both filters, it seems that nothing should come through. And this IS the case with perfect filters, where they completely pass or block. However, color printing filters are not in the class of all or nothing; they block certain percentages of light. For example a 30 cc yellow filter should block about 50% of the blue light, while allowing virtually ALL of the red and green to come through.
I really appreciate the time you spent providing me with thoughtful, and most significantly, CLEAR explanations!
You would make a fantastic teacher (if you aren't one already)!
Now your explanation has caused me to return to the issue which prompted all of this—the tamping down of a print that is "too cyan" by adding, of all things, more cyan!So lets redo the "blocking magenta and yellow" thing with 30CC filters. When we start with white light (100% red, 100% green, and 100% blue), then try to block magenta, this calls for a green filter. So after passing through our 30CC green filter, we'll find this: 50% of red, 100% of green, and 50% of blue light. The next step, blocking yellow light, calls for a blue filter. So applying a 30CC blue filter to the now greenish light, here's what happens: blue light will pass through unaffected, but only 50% of the existing red and green light gets through. Consequently we'll end up with: 25% of red, 50% of green, and 50% of blue. So the final result is that green and blue have equal strengths, while the red has been weakened to half of them.
Correct me if I am wrong, but the nomenclature for filters is what can be the source of confusion. Though we are trying to "block" red with the use of green and blue filters, each one, nevertheless, still allows enough red light to pass through to effectively neutralize at least a percentage of the cyan that would appear in the final print.
But it would still seem that the effect of whatever amount of red light allowed to pass would be overpowered by the additional cyan you have added with your use of the blue and green filters. This begs the question, why go through all of this? Why not devise a red filter, which, too, can be modified in its effects, if necessary, via the partial transmission of the other primaries?
Am I confusing things too much?