fb+fog 35mm, 120, 4x5

[mbdiesel]

Has anyone noticed consistently higher film base plus fog densities on 35mm film compared to 120 and 4x5 film?

I don't shoot a lot of tiny format anymore but I finally decided to read the fb+fog on my 35mm negs. The negs are recent 400TX and Delta 100. fb+fog on these two film type is .3. Most 4x5 films I have used (TXP 320, Tmax 100, Arista edu ultra) all read about .1 for fb+fog.

All negs are developed using xtol 1:1.

I was surprised to see 35mm fb+fog at .3. I may need to increase development times to get proper NET densities for a more full scale negative.

[BetterSense]

Well, 35mm film is thicker than 120 film it seems to me. I'm not sure about sheet film. Plus, 35mm film has no anti-halation backing so they have to prevent halation by using dyes in the base material. Maybe that affects FB+f.

[Paul Bujak]

I get B+F density readings of about 0.2 -0.3 for both 35mm (fresh APX-100 in Rodinal 1+50) and 4x5 FP4 (long out of date in Xtol 1+1). This gives PEI 0f 80 and 100, respectively. Negatives of normal scenes are well exposed and contrasty.

I developed the APX-100 for 7-1/4min at 75F and the FP4 for 6-3/4 min at 75F (Normal development).

Paul

[Drew Wiley]

Depends on the exact film, dev, and agitation method, but the different kind of base often does result in significantly higher fbf in 35mm than in sheet film.

[frednewman]

Hi mbdiesel - I've done a lot of BTZS film testing for myself and other photographers and you are correct. Typical 35mm fb+fog is from 0.25 to 0.40. Sheet film is the lowest - usually about 0.03 to about 0.15. Medium format film is just a little higher from about 0.10 and up. Yes it does depend upon the film and developer combination and development time will increase fb+fog. Both 100 & 400 T-Max seem to have the lowest fb+fog of all the film I've tested.

Fred Newman

[ic-racer]

The 35mm probably sits in your camera longer, or for some reason is not processed as quickly from the time of manufacture.

[mbdiesel]

Fred,

Thank you sharing your findings. You have confirmed what I am seeing with 35mm film. I will be mindful of these findings when I develop additional 35mm film.

Also thanx to others who responded.

Hi mbdiesel - I've done a lot of BTZS film testing for myself and other photographers and you are correct. Typical 35mm fb+fog is from 0.25 to 0.40. Sheet film is the lowest - usually about 0.03 to about 0.15. Medium format film is just a little higher from about 0.10 and up. Yes it does depend upon the film and developer combination and development time will increase fb+fog. Both 100 & 400 T-Max seem to have the lowest fb+fog of all the film I've tested.

Fred Newman