[quote="Jorge"]Shelly, I dont know but I seriously doubt Steve recommends adding 20 to 30% development time just because you switched to 120 film from 35 mm. I see no reason to do this nor have I heard anybody recommend this before. Perhaps you misunderstood?
I use FP4 in three formats, 35mm, 120 and 5 x 4, and have found that to achieve the same negative contrast I have to increase development as the format size increases. Steve's recommendation of 20 to 30% roughly equates to 1 stop, I increase development by 25% when moving from 35mm to 120 and also 25% when moving up to 5 x 4. I believe that the thickness of the film base is part of the reason.