Openness familiar to photographers (12)
I believe the answer is:
transparency
I believe this clue is a double definition.
'openness' is the first definition.
(I've seen this before)
'familiar to photographers' is the second definition.
(a transparency is a type of photographic print)
(Other definitions for transparency that I've seen before include "Photographic slide" , "Film slide" , "openness" .)