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  1. #1
    df cardwell's Avatar
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    Shaping the tone curve of a Rodinal Negative

    You can shape your film's tone curve by balancing exposure and development time with agitation.

    Agitation is used to control the highlights of a negative.
    More agitation raises the highlight density, less agitation lowers highlight density.

    In this system, development time places your shadows. Exposure places your midtones.

    It is effective to visualize comparative curves pivoting at Zone V rather than rising out of film base fog as is conventional in various systems. Introducing agitation as the third variable allows us to define any density as a 'speed point'.

    This system of exposure and development was common in the early 20th century, and was often referred to as 'standing', or 'minimal', or 'tank ' development. The principle has often been called 'compensation', although I observe that compensation is due less to special properties of developers and due almost entirely to certain films like Tri-X and TMY2 which are designed to hold information when given a great deal of extra exposure.

    NB. Standing agitation is a misnomer. Few old timers ever witheld agitation completely over long periods of time, as is often attempted today. The necessity of agitation was well documented and understood. The use in this test of 5 minute resting cycles is safe, in my experience with Rodinal, for 35mm and 120 negatives and steel reels. Some experts limit their cycles to 3 minutes. Little is gained, I have found, by using longer resting cycles while the risk of negative defects are increased.

    In the illustration are two curves which demonstrate the effect of using agitation, time, and exposure to shape a tone curve. Rodinal was diluted 1+50, and used at 68˚. The blue curve shows TMY2 developed for 11 minutes, and receiving 10 seconds of agitation every minute. The red curve shows TMY2 developed for 16', agitated for 10 seconds at the beginning, 10 seconds at the 5th minute, and 10th minute.

    The curves have been adjusted left to right to represent matching mid tones by varying exposure. I am a portraitist, and mid tones are essential to me. You may match curves however you wish.

    The red curve shows greater shadow detail, and slightly higher highlights, although in practice, the highlights print identically by adjusting the print developer or filtration with variable contrast paper. The extra shadow density is the object of the exercise.

    Rodinal is an excellent developer with this technique. You may use many other developers with this method. Pyrocat, FX2 and dilute XTOL are some of many good choices.

    *** I forgot to mention that I needed to move away from contrasty developers like Dektol to print these slightly higher density negatives.

    LPD works perfectly, and the red curve will print on Ilford FB MG just right. Ansco 130 (minus HQ), D52/Selectol, a blend of Detktol and Selectol Soft (David Vestal's Delectol !) all work well.


    I have withheld the speed rating of the test film. The intent of this short article is simply to illustrate the principle while not introducing yet another 'magic bullet'. It is better to do this work without a densitometer, and judge the results by making contact prints. After all, if you see a difference, there IS a difference. If you are interested in this method, try it out ...find your own way! You are, after all, your own magic.

    For the technically minded, the curves were created by projecting a Stouffer step wedge into a 35mm camera,
    then reading the developed strips with a graphic arts baseboard densitometer. I used a Durst L1200 enlarger, an Apo EL Nikkor lens, and a Nikon F4 camera. The film was exposed at 1/125, several negatives were read, averaged, and plotted.
    It is a remarkably flare-free system.
    Last edited by df cardwell; 12-17-2009 at 12:31 PM. Click to view previous post history.
    "One of the painful things about our time is that those who feel certainty are stupid,
    and those with any imagination and understanding are filled with doubt and indecision"

    -Bertrand Russell

  2. #21
    df cardwell's Avatar
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    Shoot a test frame here and there, Peter. You never know when it will ever snow again !

    Don
    "One of the painful things about our time is that those who feel certainty are stupid,
    and those with any imagination and understanding are filled with doubt and indecision"

    -Bertrand Russell

  3. #22
    Willie Jan's Avatar
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    What I did 2 weeks ago was the following.

    I was in an old wood factory left there for 30 years...
    I was there on a cloudy day and it rained.
    The scene had windows in it and the complete scene measured 8 stops.
    The darkest area measured was set into III.

    I overexposed my hp5 4x5 film, 2 stops. developed in pyrocat 1:1:100, 68dg for 8.5 minutes.

    The next neg was shot at normal speed and developed for 1:1:100 for 12.5 minutes which is my normal time.

    Conclusion:
    The overexposed/underdeveloped photo looks somewhat low contrast. I can see all the roof details which where in zone III.

    The normal exposed one, is crisp, fresh and does not show as much detail of the zone III. But this is how I would expect a zone III to come out. The windows need burning to get something in it.

    When I show these two pics, everybody pics the one that is normal exposed.
    So all the efford in getting all into one negative results in a worthless image.
    The sparkle is gone leaving a flat thing. The macro contrast has been contracted, but the micro contrast also...

  4. #23
    Thomas Bertilsson's Avatar
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    Why would you over expose and underdevelop on a rainy and cloudy day, with presumably flat lighting? To me that would be counter productive.

    It's no wonder most people pick the negative that was exposed normally, as it would give you enough contrast to make the print look better.

    If you shoot on a cloudy day with flat lighting and you over-expose, you still have to build contrast. That would result in a very dense negative that would be grainy and difficult to print so it looks appealing.

    I only ever over-expose if there is a lot of contrast in the scene. That's the only time it makes sense to me.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  5. #24
    Willie Jan's Avatar
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    Quote Originally Posted by Thomas Bertilsson View Post
    Why would you over expose and underdevelop on a rainy and cloudy day, with presumably flat lighting? To me that would be counter productive.

    It's no wonder most people pick the negative that was exposed normally, as it would give you enough contrast to make the print look better.

    If you shoot on a cloudy day with flat lighting and you over-expose, you still have to build contrast. That would result in a very dense negative that would be grainy and difficult to print so it looks appealing.

    I only ever over-expose if there is a lot of contrast in the scene. That's the only time it makes sense to me.
    because I got 8 stops of light and my paper is capable of showing 4.5 stops

  6. #25
    Thomas Bertilsson's Avatar
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    So how will over-exposing help, then?
    What you did was to move the tonal scale farther up the curve, and since the windows needed burning to reveal detail, your highlights got too far up the curve, into the 'difficult to print' territory.

    Either you exposed too much, or you didn't adjust your development time enough. Or both.

    It's a good thing you exposed two sheets. You came away with a nice print that works.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  7. #26
    BetterSense's Avatar
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    Why would you over expose and underdevelop on a rainy and cloudy day, with presumably flat lighting? To me that would be counter productive.
    I've stopped pushing my film on gloomy days and instead, started pulling it. I think that attempting to restore flat local contrast by increasing negative contrast through exposure and processing is a sucker's game because local contrast still won't be right but, the highlights and shadows won't fit on the paper either. In other words, if you could possibly increase the negative contrast enough to restore local contrast, its overall density range would be absurd. It seems to me that the only decent way to restore proper local contrast is on the paper. And doing so often spills the shadows and highlights off the paper. So counter-intuitively, I pull my film when it's gloomy out, knowing that I will be grabbing a #4 filter. Using the high paper grade restores a normal, crisp local contrast and the contracted negative will require minimal D&B.
    f/22 and be there.

  8. #27
    Thomas Bertilsson's Avatar
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    Well, you do what works for you. The idea with shaping the contrast curve of your negative is because you already have your paper figured out when you develop your negative. You target the paper and what it's capable of, and you know this prior to creating your negative.
    I have not done all the curves and step wedge analysis that others have, but my method is the same. Most of my negatives print with ease on Grade 2 paper or filtration, and very little dodging and burning is necessary, because I have excellent contrast and separation in the mid-tones, and the shadows and highlights naturally fall where they need to be.
    To each their own.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  9. #28
    clayne's Avatar
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    Re: Shaping the tone curve of a Rodinal Negative

    I know it's obvious - but one doesn't have to use the same paper for every negative as well.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  10. #29
    Thomas Bertilsson's Avatar
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    Quote Originally Posted by clayne View Post
    I know it's obvious - but one doesn't have to use the same paper for every negative as well.
    Nobody forces you to, no.

    In my case I use one and a half papers. One gets 90% of all negs, and then I have a second paper that I like to use for a particular project.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  11. #30
    clayne's Avatar
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    Re: Shaping the tone curve of a Rodinal Negative

    I'm just saying - different papers with different curves for different negatives with different curves. There's no way you'll successfully shoehorn everything onto a single paper - and why would we want to?
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

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