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  1. #1
    Usagi's Avatar
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    How much can you alter the characterstic curve with developer?

    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. #2
    Nicholas Lindan's Avatar
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    Quote Originally Posted by Usagi View Post
    "Although I have not made detailed tests, it appears that HC-110 tends to produce an "upswept" characteristic curve" ... What is the thruth?
    Lets go over that again ...

    Quote Originally Posted by Usagi View Post
    "Although I have not made detailed tests, it appears ...
    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.
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  3. #3

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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. #4
    Ian Grant's Avatar
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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

    Ian

  5. #5
    keithwms's Avatar
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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)
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  6. #6
    Usagi's Avatar
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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. #7
    keithwms's Avatar
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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?
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  8. #8
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  9. #9
    Usagi's Avatar
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    Quote Originally Posted by Lukas_87 View Post
    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. #10
    Lukas_87's Avatar
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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

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