A microscope let's us examine tiny things with our eyes, by maginifying them.

A similar device can be built for magnifying color differences.

Here is an example that works.

f(a, b): M * Abs(a - b)

where M is our magnification.

So given two numbers or colors, a and b, we subtract one from the other and take the absolute value. This gives us a measure of how different they are. Using a very large M, we can see the difference, expressed as a color.

Here my M is 100. I don't see much in the results, so these two values are very close.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)