Quote Originally Posted by inthedark
But I have to disagree with the newton ring part of your answer. . .newton rings appear worse when the pressure between two smooth surfaces is increased...
That is consistent. These are a products of light ray interference and it is about very small spaces and "wedges" of air or other medium.
I wish I had a nickel (US$ 0.05) for every surface I've measured for flatness and dimensional comparisons using a optical flats and monochrmatic lighhts.

I might even be able to afford photography.

Check out the color processing with short stop, and let me know what happens. I'm curious about how well my crystal ball is working.