The solder mask also has some 3D depth -- it is raised where there is copper under it. You can shine a surface light (no need to be bright) at an oblique angle to see the edges of traces, even when covered in conformal coating. My ceiling light was adequate for this purpose, for me (on the PW2). Though a bright light helps see traces a layer down into a mult-layer PCB, and shining the light THROUGH a board from the backside helps follow some traces too (as long as ground and power planes do not block the light). I seem to recall that you talked about this in a post somewhere,
knc1.
But for the serial traces on a PW2, plaining visible right there on the surface, snaking under a metal RF shield. With skill, they could be soldered to without removing that shield, if not peeled off along with the pads.
And yes, you can do gamma adjustments to a photo to bring stuff out of the shadows. RAW photos allow much more adjustment than JPEG does, so set your camera to save RAW images if it can (or hack it with "Magic Lantern" or CHDK to add that feature). Yes, I have run a "hello world" on my EOS-550D camera, which now has tinyCC in its firmware image. It even has a built-in fisheye dewarping app, now...
