Current reciprocity champion in 4x5 sheet film

[loccdor]

The inherent problem once you get deep in reciprocity territory is that contrast runs out of control and you end up with an escalating "more exposure,less development" situation. That's a kind of mathematical limit you run into.

Since we're talking about the shadows being more impacted by reciprocity in a long exposure than the highlights, I'd bet the point where you reach that mathematical limit could be extended with a film pre-flashing.

 

[koraks]

Yes, indeed, a little.

 

[DREW WILEY]

Pre-exposure was once used to increase the sensitivity of astronomical plates. But in general photography, pre-flashing can simply make the shadow separation and texture go blaah if not very careful done. It's like creating a longer muddier toe to the film.

Sounds like a fun experiment however, for those with spare film and time to waste. Once in awhile I do selective pre-flashing with color film to control unwanted hue casts in shadows; but I've never had a motive to do it with black and white film.