Acceptable Fog Level. fb+f

[lhalcong]

What is an acceptable Fb+f level for B&W film. In my case I am talking about Tri-X 400 and TMAX 100/400) . Developing under my NORMAL Conditions for my standard process, I've been getting fb+f level anywhere between 0.22 and 0.29 . my Tri-X 400 is usually in the 0.25 to 0.29 range and my TMax is usually in the 0.22 to 0.26 range. I couple of days ago I processed a Tri-X roll that was 6 years+ expired (not refrigerated kept inside A/C home) , exposed about two months ago. I processed Normal. Fb+f was 0.40 which I expected. At what level does it become a problem ? and what is good fb+f level.?

thanks in advance.

 

[snapguy]

venture

Might I venture to say that any fog level for expired film is negatives that let you make a pretty good print?
I don't know, is more fog level okay if you have photographed a boat on the river in the fog? And not okay if you shot the photo in broad daylight at the beach? I think perhaps some things can't be measured on an instrument.

 

[Bill Burk]

It's important to know if this is 35mm or another format. On purpose, 35mm has more base density than sheet film. I don't know the spec, but over 0.20 seems reasonable.

TMAX-400 sheet, I get B+F of 0.05 because the base is "clear".

 

[Xmas]

we are only interested in the exposure that gets a density say 0.1 more than the fog because that what gets shadow detail on the print.

So you need a step wedge and exposure.

If you then do sets of increasing time in developer & when the fog level rises at the same rate as the step wedge image you are over developing - try more potassium bromide or BZT.

A developer needs to keep both the fog level low and contrast low to increase useful film speed unless you don't need highlights.

Microphen is better than ID11.

If you cook film the fog level increases.

 

[lhalcong]

I shoot only 35mm.