Did I miss the part where the type of film was mentioned? Are we talking Rollei, Efke SFX200 or HIE? All are going to expose differently through cutoff filters depending on their sensitivity... The Efke 820IR I'm shooting at ASA1, and developing in TmaxRS at standard Tmax100 time. 072 filter. That gives me an outdoor, bright sun exposure around 2 to 4 seconds at f8 or f11. I never bothered to shoot HIE through a cutoff filter because a 29 plus polarizer gave me all the contrast I wanted. I have samples of the efke at: http://www.flickr.com/photos/schafphoto/