what does it mean when it said to develop N+2 stop?greenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
I have read books saying that in the zone system expose for the shadow and develop for the high lights.....meaning the developing time as Normal time plus 2 stop. I don't know what 2 stop is. What is the time of this 2 stop plus developing time?
-- ruiko Carll (email@example.com), March 12, 2002
N+ development is when you extend the time of development to increase the contrast of the negative (think of it as expanding the range of tones). Higher zones (brighter areas of the scene) continue to develop more density with longer development, whereas lower zones (dimmer areas) will only go so far.
To drop into 'Zone System' speak (see below), N+2 means that a negative with an area exposed at Zone VI will be developed to Zone VIII, a two zone (or stop) increase.
Another way to think about N+/N- devlopment is to imagine the tonal scale is a rubber band. You can stretch the rubber band and expand the range of tones by increasing the development time. Likewise, you can shrink the rubber band (reduce contrast) by shortening your development time.
To properly find out what your personal N, N+ and N- develoment times are, you need to do some testing. I would strongly recommend reading Ansel Adams 'The Negative' - it describes the above topics much better than I can. In fact, what you're really interested in is the "Zone System' of exposure. Ansel Adams was one of the creators, and it's pretty much the base of all B&W photography.
BTW, when I say personal, I do mean 'personal'. Every person works differently, has different equipment, and uses different films and developers. Only through testing can you determine what YOUR development times are. Testing, even at it's simplest, *will* yield better negatives.
Lastly, while you can use the Zone system with rollfilm, it's really more suited to sheet film where you can develop each sheet differently. With rollfilm, you're left with developing the entire roll the same way (treating every frame as if it has the same contrast). Some people who use medium format cameras have multiple backs, one each for N-1, N, and N+1 development. For 35mm, you may need to use multiple bodies, or just swap out your film. Not very practical.
Hope that helps.
-- Ken Miller (firstname.lastname@example.org), March 12, 2002.