Because of their highly-polished, mirror-like fields, proof coins require special attention. The preferred lighting method, known as axial lighting, is able to illuminate the troublesome field evenly, without reflections. Modified versions of this technique can be used to add depth and character.
As the name suggests, this technique leaves the field dark, illuminating only the relief. Not as useful commercially, dark-field lighting is more appropriate for collectors who want to fully appreciate the relief detail.
This Zachary Taylor dollar was photographed using simple side-lighting. The only editing done to the image was a shifting of it's black-level to deepen the black and eliminate any stray flecks of light in the field.
Proof coins are often advertised using a partially-darkened field. This effect can be achieved a number of ways, including the use of multiple images. The contrast between light and dark presents an implied luster.