Push/Pull Exposinggreenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
When film is said to be N-1 or N-2 does this simply mean (Normal minus one stop..etc.)? Also, when one uses a spot meter...is there a quick formula to calculate these exposures..i.e. You meter an EV of 14.5 to 4.5 how do you determine the correct settings for N-1 or N-2?
-- Darrin Young (Aleedar@excite.com), March 07, 1999
For 'N-1' read 'contract by one zone'. Similarly, 'N+2' means 'expand by one zone'. Roughly speaking, developing for N-1 means reducing the contrast of the film (by reducing development) so the effect on the film would be as if the scene had one zone less contrast.
In your example, the scene has a contrast range of 10 zones (14.5- 4.5=10). If your film can handle 10 stops, just develop as N. If the film can normally only handle 9 stops, develop as N-1. Etc.
For a real explanation, see Adams 'The Negative'.
-- Alan Gibson (Alan.Gibson@technologist.com), March 08, 1999.