Quote Originally Posted by BobF
Phil, the Ilford site lists an anti-halation backing for roll (120) and sheet film but none for 35mm. Makes sense as presoak of 35mm pours out clear while presoak of sheet and roll pours out black. I use all three types of FP4.

The acetate they use on 35mm has some kind of tinting that isn't on the roll or sheet film but to me it looks neutral grey, not blue. Densitometer readings on roll and sheet film (FB+Fog) are half that of the tinted 35mm acetate. Readings of .16+/- for roll and sheet versus .32+/- on my old analoge weston densitometer.

Don't ask me why they do this or what affect it has, but if anybody knows please chime in.
BobF, Thanks for reading the density differences in the differing formats. I thought that I remembered that 35 mm carried a higher FB+fog then sheet film. As I recall the reason that I was given for this is that 35 mm uses a thicker polyester support. The tint that you noted would certainly contribute because it would act as density. The thicker support may be used because the physically smaller film would be more prone to distortion then the larger physical size of sheet film.