Yes pre-flashing (or post-flashing) lowers paper contrast. Both pre and post-flashing can put uniform fog on the paper if done incorrectly (or if that is the intent - which it occasionally is). Perhaps what you're missing here is the procedure. Assume you want to pre-flash. You first do a test strip using non-image light and find the longest exposure time that does not result in any print density/fog. That is your pre-flash exposure. Then you incorporate the pre-flash into all further test/work prints. Since you're determining your image exposure with paper that has been pre-flashed, the pre-flash exposure is taken into account when you find your print exposure. So there is no unwanted fog.
Originally Posted by cliveh
Post-flashing is harder because you have to work backwards, first determining the maximum amount of image exposure that yields no highlight density, then finding the amount of post-flash required to just bring in the highlight detail from the image exposure. If done correctly the end result would be the same as the pre-flash (although the flash exposure time might not be the same). Since the end result is the same as a pre-flash, and the pre-flash procedure is easier/more intuitive, I can't really envision a situation wherein one would post-flash, unless it is part of a broader sequence of masked exposures.
Bottom line is that wherever you flash, you lower paper contrast. So in general it is a much less useful technique with VC papers than with graded papers.
Last edited by Michael R 1974; 10-15-2013 at 08:50 PM. Click to view previous post history.
Reason: tried to be clearer