Tmax 100 strange grain or dots

Discussion in 'Black and White' started by brett_kosmider, Sep 28, 2006.

  1. I initially thought this was a scanning issue but after some investigation it is clearly a film issue.

    For the last two years I have shot a lot of 120 format Kodak Tmax 100 film. I do a lot of long exposure
    work as well as normal exposures. All film was exposed with a Mamiya RB67 ProS with a ProS back and a
    ProSD back. AUp until now I have my film processed at a lab.

    My problem is that on some scans I will get a pattern of large dark "grain". These grains are larger than
    the film grain and they appear as a very distinct uniform pattern. Upon very close inspection under a loupe
    it is evident the dot pattern is in the negative (as white dots). I am unsure if the dots are being introduced
    to the film in the exposure or in the processing.

    If it's the exposure I wonder if it only occurs on the long exposures - most between 50 seconds and 5
    minutes. I have not encountered any of the dots on normal exposures (under 1 second)

    If its the processing, what to do?

    I have yet to test a different film (I will soon though, I was thinking Fuji Neopan Acros 100 just to see what
    happens). Perhaps I should change labs as well. I have even suspected my differing film backs.

    See sample below



    Any help is appreciated.

    Brett Kosmider
     
  2. I'm not familiar with your camera, but is it by chance, that the film is picking up the impression of the pressure plate, on long exposures?
     
  3. Brett, It sounds like air bells from lack of agitation or not vigorous enough agitation. Could you provide a scan?

    You say it is white spots on the neg that goes with my theory of lack of devolvement in those areas where the air is clinging. Do you give the tank a firm rap on the counter after each inversion or at least upon pouring all developer in?

    Good luck.

    ,Grinder
     
  4. I see the scan now. Sorry for the dumb moment.
     
  5. Wow. Something new every day. Strange it only shows on long exposures. I would suggest you do some short and long exp one roll to see if it only shows on long. Even than be wary as the stock may change more and begin to show on short exp too.
     
  6. At one point I thought it might be the pressure plate, but the matrix of dots doesn't seem
    to line up and is diagonal in nature. I wish it was the pressure plate, that would be an easy
    fix!

    When the conditions are right (I need a scene with a large area of graduated gray, like a
    blue sky) I will do the following test:

    One roll of Tmax 100 - shoot alternating frames between the metered time of, lets just
    say 1/15 and the next frame at 2 minutes (with appropriate ND and accounting for
    reciprocity)

    Then do the same thing with Fuji Neopan Acros 100

    I think I'll do that twice and take one roll of the Tmax and one roll of the Acros to two
    different labs in town. Then see what happens.
     
  7. I'm inclined to agree with Stephen. The pressure plate in the RB is dimpled and the pattern fits that of the artefacts on your negative. Quite why it should happen is another matter since the backing paper, I would have thought, should prevent such reflections. I can't remember whether I have done any time exposures with my RB longer than, say, eight seconds, but I've never had this problem.

    Try an Ilford film such as FP4 and see if the problem disappears.
     
  8. Here's a thought - could it be that Tmax 100 is slightly sensitive to a portion on the infrared
    spectrum? Normal exposures might not register that sensitivity but a long exposure of many
    minutes in a daylight situation might register the infrared "reflection" off of the dimpled
    pressure plate. Just a thought. Am I crazy?
     
  9. Brett,

    I think you might be on to something there. It would be informative to look at the spectral sensitivity curves of TMX and, say, Ilford FP4.
     
  10. I just processed a roll of T-MAX 100 of the same vintage (shot in mid-2005, exp 07/2007) and see the same very regular
    dot pattern on the negative under a loupe. I don't think this has anything to do with the camera or the processing. Unless
    waiting *ahem* a while to process it was a problem. I think this is could be a defect with some samples of film from this lot,
    although another one from the same lot shot and developed in 2005 did not have the dots. The lot number is 0531 002 (on
    the box and imprinted along the film edge).
     
  11. Please refer to the more current thread for responses:

    http://www.photo.net/black-and-white-photo-film-processing-forum/00QXPB
     

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