high base fog

Discussion in 'B&W: Film, Paper, Chemistry' started by rmolson, Jul 23, 2013.

  1. rmolson

    rmolson Member

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    Base density level


    Getting back into photography after a two year absence. I have been getting overly heavy negatives on my 35mm work So I ran a whole zone test Using HP5 rated at 250 in Claytons F-76 1:9 I got a base fog of .28!!! Which put my zone I at .50 .28 =.22. Obviously why off. I checked on both of my densitometers and they agreed. The calibration strip was spot on,.I use to do this for a living. The House is not air conditioned and the temperature got up in the 80s this summer How resistant to heat fog is HP 5? Claytons F-76 is suppose to be similar to D-76 and I never got base fog this high with D76 on Tri X.
     
  2. cliveh

    cliveh Subscriber

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    This may be over development.
     
  3. selmslie

    selmslie Subscriber

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    Try a fresh roll of HP5 and fresh developer. Heat and other factors may have fogged your film.
     
  4. michael_r

    michael_r Subscriber

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    I haven't tested HP5+ in particular, but with FP4+, Delta 100 and Pan F+ I normally get a film base+fog reading of ~0.30, which is normal for me with Ilford films. I get lower film base+fog levels with films like Kodak TMX/TMY (around 0.20). Ilford films simply have a higher base density. No problem.

    Your zone I on the other hand seems high, although be rating the film at 250 you're giving nearly an extra stop. Hard to diagnose however without more detail regarding your film speed/testing process.
     
  5. Bill Burk

    Bill Burk Subscriber

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    4x5 films tend to be manufactured on "clear" base, while 35mm films may have a "base tint" for antihalation purposes.

    rmolson, have you ruled out what you see isn't just normal base tint?
     
  6. rmolson

    rmolson Member

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    IF .30 is normal base density for HP5 then my reading make sense. Just use to much lower base density from sheet and roll film. Will need to adjust development times though.