Coming from digital (I'm sorry, I have seen the light in only 2 rolls and I apologize for my many digital sins over the past 2 years ) I'm a bit confused about film speed, it seems much more subjective in metering, perhaps I am missing something but when I shot with my digis it was always set the ISO and meter for what its set. However I seem to be reading all kinds of stuff aobut people exposing at a different film speed then the listed, what is the reason for this? Is it coupled with expanding and contracting in development? I had thought that epanding and contracting delt only with contrast and though required slight exposure adjustment I dont think thats what this is. Is it simply finding what the "acctual speed is with your meter/lens/bellows etc.? Or is there something else I'm misisng? Any recomendations would be appreciated, I'm am working my way through AA series, finnsihed the camera and aobut halfway through the neg. In the appendix he tests for effective film speed (I think he uses a different term) but once that speed is found, is there still reason to shoot at a different speed (pushing and pulling in development would be one I suppose but if I have the light I need to get the exposure I want at the shutter I need would this ever be superior?) I guess I'm getting the feeling that film speed is mroe subjective in analog than in digital, is that true? If so why? Thanks for the help.