Duck wrote:Sometimes looking at a problem with fresh eyes is the best thing to solve a problem. After reading your last post the only additional thing I can offer is to not get overly hung up on a one setup fits all situation. Think of it more as a one size fits most but allow for variances (like in this case).
For this kind of work I would not suggest HDR as the issue is not exceeding your exposure range. Specially since you are in control of the range with lights. It's rather a light control issue. In particular, refer to Ed's notes earlier in this post, specially about light fields and my own tutorial on "Understanding angle of incidence". Both of these hold clues on how to solve this issue in the future. While this inversion method can work on silver coins, it will not prove as easy with gold coins.
Another trick is to use live view and, while looking at the display, move a flashlight around and over the coin until you find a suitable angle that works. That will also give you a cue as to where to place your lights.
Thanks Duck. I'm hoping to avoid compositing or HDR. If this coin had two surface textures then a straight out dark field approach would be my direction. As you can see by the 180º change in tonal values between the previous attempt (before the inversion) and tonight's approach getting a positive result in one area negatively affects another. The differences in elevations and angles are minute and occur a hair's breath away from each other.
For sure there isn't a one button fix. There are some general rules of thumb for various textured and finished coins. I like the chipping away at the possibilities and seeing what happens.