PMK Question

Discussion in 'B&W: Film, Paper, Chemistry' started by RAP, Sep 18, 2003.

  1. RAP

    RAP Member

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    I have been developing some film this AM with Hurricane Isabele effects blowing outside.

    The TRI-X 4x5 sheet film stained very nicely, developed in HP Combi tanks.

    However, the Ilford PanF Plus 120 did not stain even half as much. Also the 35mm PanF Plus did not stain at all. Both rolls were developed together in tanks, agitated 2 inversions ever 15 seconds, with 2 minutes in the used developer, agitated ever 30 secs.

    Why the difference in stain, especially the 35mm?
     
  2. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Simply, some films stain better than others. Tri-X is one one of the films that develops a stronger stain.
     
  3. RAP

    RAP Member

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    Yes I understand that. But what is confusing is why should 120 and 35mm Pan F Plus stain so differently when processed at the same time.
     
  4. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    The base is different, and the antihalation dyes may be different.
     
  5. Aggie

    Aggie Member

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  6. Black Dog

    Black Dog Member

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    Faster films generally stain better than slower ones (more silver as previously mentioned). You might also try lengthening the after fix soak in the used dev, or using stock solution that's been well aged-the latter worked well for me.
     
  7. Aggie

    Aggie Member

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  8. Donald Miller

    Donald Miller Member

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    There has been so much in conflicting opinions bantered about that I decided to conduct tests of what the staining effects amounted to with PMK developer. These tests were verified by using an Xrite 310 densitometer.

    First of all we must determine what aspect of stain that we are speaking of. If we are talking about proportional stain then the tests would support that development in PMK and other Pyro based developers does indeed depend on silver density on the negative. This silver density is more a function of exposure and development then it is of the matter of whether a film is more or less "silver rich" (whatever that means.) I did not find that the effects of the proportional staining was dependent on film manufacture or film speed so much as it was a condition of the density of the negative. My tests indicate that the effects of proportional staining typically add nearly .28 (when read through the blue channel) to a negative as compared to a visual density reading of 1.20. The effects on UV transmission are still greater. The effects of this proportional staining are not readily discernable to my eye. I have determined the effects of proportional staining on not only TriX, but also FP4, Bergger BPF 200, and JandC Classic 200. The effects of proportional staining on various films is typical very near the same at a given density with a given developer.

    If we are speaking of general stain as compared to proportional stain. (of which most people seem to be speaking) the staining effect is discernable to the human eye and is not proportional (in and of itself) to silver density of the negative. This would tend to indicate that the presence or degree of this general stain is not as dependent on film type (it's relative speed etc.) as it is upon film base material and of the carrier in which the silver emulsion is suspended.

    This is born out with testing experience with 35 mm film in comparison to sheet film. The base material of 35 mm exhibits a density reading of .15 film base and fog as compared to .04 with sheet film in the case of TriX developed in the same developer. The unavailability of proprietary information from Kodak as to the base material characteristics does not enable me to evaluate whether the cause of the general stain effects attributed to PMK are those of the film base material or of the emulsion carrier material. It quite apparently must not be due to the amount of silver or of the film speed. The reason is that the general stain exists in regions of low silver density (TriX sheet film) and not to the same extent on the Tri X film in 35 mm format. It is interesting that this film (TriX) is not a slow speed emulsion and that the film manufacturer is the same in this case.

    In the use of pyro developer formula ABC we can reach a point in development at which fog levels increase to the point that the effect is one of effectively inhibiting the contrast within the negative. This fog development does not occur as rapidly with Pyrocat as it does with ABC. In the case of PMK or for that matter any developer that exhibits the tendency to impart general stain the effects are akin to the formation of general fog as I have indicated above. The formation of general fog and general stain have the same generalized effect that being the inhibition of the full potential of proportional staining.
     
  9. fhovie

    fhovie Subscriber

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    It truely is the combination of a certain film, developer and film format that is the choice - PMK and -any staining tanning developer is going to perform best on specific films.
    Frank
     
  10. sanking

    sanking Member

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    Donald,

    Interesting observation, and I agree with most of your findings. A few comments.

    1. If you would like to test the base material of the film independent of the emulsion you can just strip the emulsion off and then measure the base. To do so just place the film in a solution of Clorox and after a minute or so you will be able to easily rub off the emulsion, leaving nothing but the polyester base.

    2. There is a big difference in the transmission of the base of some films, especially in the UV range. Just compare the base of TRI-X with TMAX-100 in UV reading, for example, if you really want to be blown away.

    3. To repeat what I have said before, which your tests show, is that proportional stain is the stain that is formed around the silver grains. It is very desirable and adds considerably to the micro-contrast of all films that are based on silver.

    4. General stain affects the entire gelatin layer, regardless of whether there is silver density or not. It is nothing but extra fog density and serves no useful function, and under certain conditions is harmful to maximum image quality.

    5. From the above one should conclude that staining developers work about equally well with all films that contain silver. That some films appear to work better than others is due to fact that the gelatin base of some films is thicker than that of others, and this films consequently develop more general stain, for the simple reason that there is more gelatin to stain.

    6. Irrespective of anything you or I may say on the matter there will be many who continue to believe that a high level of general stain is desirable. But that should surprisse no one. Myths can be powerful things.