How much can you alter the characterstic curve with developer?

Discussion in 'B&W: Film, Paper, Chemistry' started by Usagi, May 24, 2009.

  1. Usagi

    Usagi Member

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    The interesting question came to my mind after I ran into this writing at the internet: http://www.imx.nl/photo/Film/Film/Film/page39.html

    According to writer, Erwin Puts, the developer does not have (any) practical effect to the film's characteristic curve.

    This site states exactly opposite:

    "Although I have not made detailed tests, it appears that HC-110 tends to produce an "upswept" characteristic curve with relatively high contrast in highlights (dark areas of the negative, light areas of the picture). With T-Max 100 film in particular, HC-110 produces an upswept curve, with more contrast in the highlights than in the shadows, while Xtol produces a more S-shaped curve (reminiscent of Tri-X Pan), with the most contrast in the midtones."
    I have always thought that developer have and different developers alters the shape of the characteristic curve.

    What is the thruth? Is there some more documented facts about this?

    Have to say that I have not never run sensitometric tests to same film with different developers... Perhaps I should do so.
     
  2. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Lets go over that again ...

    That should answer the quandary.

    That said, some pathological developers do have an effect on the characteristic curve; as an example, Rodinal produces very low shadow contrast.
     
  3. Carter john

    Carter john Member

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    I probably know less about this than you, but I have wondered about this for years (and tried to study it). I also read the Covington statement years ago, and was a little disappointed as I use a lot of TmaX100 with HC-110. I really hope someone jumps in here with some answers.
     
  4. Ian Grant

    Ian Grant Subscriber

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    Developers are used routinely to alter the characteristic curves of film and paper. There's a vast array of low, medium and high contrast developers around.

    Typically low contrast developers are used with micro films to tame the contrast, high contrast or even lith ype developers to produce extreme contrast then a plethora in between.

    Unfortunately those writers don't know what they are writing about :D

    Ian
     
  5. keithwms

    keithwms Member

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    Yeah I don't see why someone would say that you can't affect the curve with a developer. Don't we do it all the time? We do know that we can affect the CI via dilution and time and agitation etc...

    Offhand I'd guess that combinations of different developers (and dilutions) can do just about whatever you want with the extremes of curve. I see no fundamental reason why development should proceed at equal rates in the shadows and highlights, so, in principle some combination of noncompensating and supercompensating developers, or perhaps merely multiple baths with different dilutions, should give some curve control.

    What comes to mind the documented effect of warm water bath stopping... which I suppose could be argued to manipulate the curve via the action of residual developer in dilute form.

    (these are merely offhand thoughts, others like Ron can surely provide better info)
     
  6. Usagi

    Usagi Member

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    What should be noted is that CI is different thing than the shape of the curve.

    When keeping CI constant, how much can we affect the general shape of the curve by varying only the developer? Does some developer give more contrasty highlight (straghter shoulder) and some other developer give flatter?

    Does some developer with given film give different shape to the mid tones and thus affect the separation of the middle tones?
     
  7. keithwms

    keithwms Member

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    Well, CI determines the compression of the tone scale, so if you control that in tandem with control of the degree of compensation, wouldn't that amount to curve control?

    And like I said, some developers and concentrations will affect highlights at a different rate from shadows (as proven by warm water bath stopping), so... isn't that curve control?

    Or do you mean something more extreme?

    Indeed you probably can't affect the highlights totally independently of the shadows and vice versa, but still we do have some relative control. I can see where the case is harder if you are restricted to one developer, but... there's no law against using multiple baths with different dilutions, or using more than one developer (e.g. compensating and noncomensating) in different order.

    Maybe I am missing something?
     
  8. Lukas_87

    Lukas_87 Member

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  9. Usagi

    Usagi Member

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    Thank you for the link. Seems to be lot of information there.

    As I quickly looked, for eg. Delta 100 will have quite similar S-curve regardles of developer (FX-39, Rodinal, Xtol).

    Have to look more closer though.
     
  10. Lukas_87

    Lukas_87 Member

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    many combinations of film+developer are listed there, with densitometric graphs.
    every film were developed for normal contrast so these graphs can ansver your question definitely.
    http://www.fotoimport.no/pg02/pg02-1-1.htm
     
  11. Lukas_87

    Lukas_87 Member

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    sorry for double post, I thought it was not posted correctly...

    actually - a lot of the modern emulsions (Delta 100, 400, 3200, Neopan 400, 1600) have compressed characteristic and the developer used only affects intensity od compression or actual emulsion speed (measured on ISO standards).
    older emulsions tends to be compressed too, but at higher densites (3-4) so it is extremely hard to make compressed image with them and to print it, of course.
     
  12. richard littlewood

    richard littlewood Member

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    If you operate the zone system the N-, N, N+ development along with the altered exposure values is quite a neat way of tweaking the curves.
     
  13. dwdmguy

    dwdmguy Member

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    I may finally have an advantage over you guys....
    I'm a relative novice in the darkroom, only the last year, and I clearly see a different curve using different specific developers.

    FWIW
     
  14. Usagi

    Usagi Member

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    I mean the shape of the curve. Yes, CI defines compression but CI is just one form of average gradient, thus two different films with complete different curve shape can have same CI.

    Now, having more time to study link I found something that actually shows what I am looking for: The shape of curve can be altered by developer. At least some degree.

    Here's the APX-100 developed in FX-39:
    [​IMG]

    And here's in Rodinal:
    [​IMG]

    And Tmax:
    [​IMG]

    The overall shape of the curve is S with these developers, but with rodinal, the shoulder is much straighten than with FX-39 and TMAX. That is kind of differences I am looking for.

    However, the really interesting is differences of middle tones - 'the straight' section.
    Can it altered to be more unswept, or curved? According to new edition of the Adams's Basic Technique Of Photography Book 2 and various web sites - Yes. Mainly with HC-110 which gives unswept curve for films that usually has S shaped curve.

    So far, it seems that Puts website cannot taken seriously. These all shows that curve shape is not entirely defined by emulsion of the film but developer also has own impact to it.

    But how far we can go and with which film and developers? Can straight charasteristic curve (like curve of TMAX 100) altered to have both, more curved toe and shoulder?


    This is interisting issue, I have calibrated lot of films for ZS, drawn charasteristic curves, studied them etc... But always with one developer + film combo. Never had time or interest to do same test for given film with another developer. Except one case: when I changed D-76 to XTOL, I had to recalibrate developing of some films, but with XTOL the shape of the curve didn't changed.
     
  15. Lukas_87

    Lukas_87 Member

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    it is important to not overdevelop too much because you will get high density negatives with shoulder as like the apx100 + rodinal (you can be sure the shoulder IS there but far far away from easily printable range of the negative)
    talking about this - friend of mine never had a problems with printing the lightest areas, never needed preflashing and other tweaks.... why?
    everything on his negatives is straightly printable.... he uses delta 400 + dd-x at most. sometimes tri-x 400 in microphen od neopan 1600. nothing else at all.
     
  16. dancqu

    dancqu Member

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    And any one of them, according to the manor in which
    it is used, will allow for curve alteration. Dan
     
  17. ic-racer

    ic-racer Member

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    Here is an example of what Nicholas is describing. Same film, two different developers, similar gamma:
    [​IMG]
     
  18. nworth

    nworth Subscriber

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    In many cases, the differences are quite significant. Also note the differences in film speed for the various developers.
     
  19. Usagi

    Usagi Member

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    Rodinal alters the toe that much! That was new to me. Thank you!
    (actually same information is on the on the chart's of the Foto Import site if I take my eye to the hand and look closer)

    Now I have really something to study and test. Should even do some testing with my mostly used films with rodinal, xtol and pyrocat-hd. Then I will be wiser - I hope.
     
    Last edited by a moderator: May 25, 2009
  20. dr5chrome

    dr5chrome Member

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    How much can you alter the characteristic "curve" with developer?....

    ENORMOUS!

    Mr. Puts is quite wrong, if this is what he meant.
    Its possible what he meant was the "character" of the film is unchanged.

    Regards

    dw




     
    Last edited by a moderator: May 25, 2009
  21. john_s

    john_s Subscriber

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    And if you use a staining developer and have a choice between graded and VC paper, you effectively have two different curves. The VC paper will introduce a rolloff for dense parts of the negative (because of the filtering effect of the colour of the stain), and the graded paper will not.
     
  22. keithwms

    keithwms Member

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    Is that because the stain acts essentially as a grade filter?

    I've not seen this with wd2d+, though I understand its stain is quite different from what you get with many of the more popular pyros.
     
  23. Thomas Bertilsson

    Thomas Bertilsson Subscriber

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    This is probably why you want to overexpose negatives that are developed in Rodinal, to place your shadow values on a straighter portion of the curve. That way you can benefit from the rest of the characteristics of Rodinal.
    The toe of the Rodinal / Tmax comparison, to me, simply indicates a loss in film speed, and is probably the reason why I preferred, for example, Kodak Tmax 100 exposed at an EI of 64 or so when processing in Rodinal.

    After many years of fumbling in the dark, I am finally starting to understand how film developers work, and it seems to me that as you alter agitation (and therefore, indirectly, you alter time) both your midtones AND your highlights are affected by it. The more a particular part of the negative is exposed to light, the more sensitive it becomes to changes in agitation.
    So as you alter the shape of the shoulder by altering agitation, your midtones 'follow'. I don't know if there's a trick to separately treat just the mid-tones, to me they are more indirectly altered by a combination of exposure (metering) and the decisions you make to make sure you get printable highlights.

    - Thomas


     
  24. Alan Johnson

    Alan Johnson Subscriber

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