Tough question. Unfortunately no exact answer that I know of. The problem with the Ilford chart is it is generic (ie they use the same chart for most if not all the films) and somewhat out of date. Howard Bond did some helpful testing around 10 years ago with sheet film but Pan F+ was not one of the Ilford films tested. There are also various equations around - but again these are generic, not film specific. I know of no other graphs or charts based on hard data, although there is a lot of anecdotal flim flam out there if you're interested
Originally Posted by grantlyd
I would say use the Ilford chart as a starting point (it will likely overcompensate) and do a few experiments. Also, luckily, Howard Bond's tests showed that contrast increases with long exposures are not as pronounced as they once might have been, so that's kind of helpful particularly if you overcompensate.
As for using a different film, you will have the same problem, but there are a few generalizations that can be made: 1) tabular grain films such as Ilford Delta and Kodak TMax need less reciprocity compensation than "conventional" films like Pan F+, FP4+, Tri-X, HP5+ etc (although the current versions of these films need less compensation than earlier incarnations). Fuji Acros (another tabular grain film), which was mentioned by Early Riser, is a special case in that it needs virtually no reciprocity compensation for exposures up to two minutes, and much less compensation than other films for exposures longer than that. 2) slower films like Pan F+ will tend to be trickier to use in night/low light photography because these tend to be high contrast shooting situations and slow films like Pan F+ usually have higher contrast and/or a shorter scale than most medium speed or high speed films.
Basically, if you're getting into night shooting, you'll have some experimentation to do, and it will take some practice. Most of my photography is done at night or under other low light indoor/outdoor conditions, often involving very high contrast subjects/lighting (night scenes with light sources like lightbulbs, street lamps etc in the frame). It takes practice, regardless of which film. I've used mostly TMX/TMY and Ilford Delta 100 for this work (I did some extensive testing of Acros but in the end went back to Ilford). These are just my personal preferences though.
One more thing - don't make the mistake of assuming a film needing less reciprocity compensation is a "better" film. It doesn't work that way at all.
Last edited by Michael R 1974; 04-29-2013 at 08:15 PM. Click to view previous post history.