How Direct Positive Photography Works – Why Silver Can Look Black or Bright
One of the most fascinating things about silver-based photography is that the material forming the image is, chemically speaking, surprisingly simple. Whether we are looking at the dense black areas of a conventional negative or the brilliant highlights of certain direct-positive processes, much of what we see is ultimately metallic silver. Yet the same element can appear deep black in one photograph and almost white or silvery in another. Understanding why brings us into a particularly interesting part of photographic chemistry, where chemistry, particle growth and optics all begin to overlap.
Why is silver black in the first place?
A photographic emulsion...