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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. #11
    df cardwell's Avatar
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    An example of a 12 tone palette

    A friend read this and asked the reasonable question, "What's different about a midtone based system from a Zone I based system ?"

    I replied in a knee-jerk way, "Well, you can go straight to the shooting and not worry about fine tuning the exposure."

    And then I realised that wasn't the BIG THING for me. The BIG THING is that meant I seldom need to burn and dodge a print. The scale of the scene fits the scale of the paper.

    But the BIGGEST THING is that the midtone contrast, the LOCAL contrast, would be correct without mucking about. And then I remembered something David Kachel wrote (more years ago then I care to remember) about LOCAL CONTRAST. PLease take a look, David has left this online for you:

    http://www.davidkachel.com/historical/prilclct.htm

    And here is an example of an incident reading of an extremely long scale image, rendered in 12 tones, that prints on a normal paper with no gymnastics. The compensation takes place at the extremes of the scale, while the midtones are a straight line. THAT is the difference between this method, and conventional control systems. You can go straight to the shooting with a simple incident reading, and not need to burn and dodge to fit the scale on contrasty paper to hold local contrast.



    .
    "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. #12
    bowzart's Avatar
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    DF, I appreciate the Kachel a lot. I began to notice this, oh, I guess in about 1965. Of course I've developed my own now rather instinctive ways of dealing with it which certainly have something in common with what you are suggesting, but still generally dealt with by more typical exposure/development controls. I tend to set my exposure where I want it, which often is not what straight shadow readings would indicate - exposure with a visualization of the whole curve. Then, I make a determination of the development which also might not conform. Having used the ZS for something like 45 years, I have a rather hefty intuitional tool set which generally serves me well. Getting to know your agitation methods has been quite interesting and I have been employing them (insofar as I'm able to work in my presently rather limited circumstances).

    Anyway, thanks, and I'm going to keep these at hand. I'm reading philosophical text right now, and I have to say, Kachel is about as clear as Plotinus, but it's getting better on both sides of the equation.

    L

  4. #13
    markbarendt's Avatar
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    Wow DF, great stuff. I need to do some testing!

    Pardon me if this is simply restating the obvious here or correct me if I haven't got the concept.

    Using this method I should be able to (within certain limits);

    1 - Place my exposure based on what is best for my subject on any given film.

    2 - Decide how much shadow detail I want in relation to my subject and adjust this with development time.

    3 - Decide how much highlight detail I want in relation to my subject and adjust this with agitation.

    So, for a back-lit afternoon portrait I could;

    1 - set the camera by using an incident reading "under their nose" to place the main subject on the film exactly where it needs to be to print nicely,

    2 - then extend or reduce development time a bit to control the details in the bushes behind them, and

    3 - enhance or reduce my agitation to control the details in the sky.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  5. #14
    df cardwell's Avatar
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    That's pretty much how it works, Mark.

    There ARE limits. The film, for one thing. TMY & TX are great for this. TXP, not so good.
    Neopan 400, not good, for different reasons. FP4, great.

    It will probably be sufficient to make 3 all purpose negatives. My 'Sangre de Christo' negative would have normal contrast from IV to VI,
    and would run out from there. You've got the idea perfectly, as well as live in a place where it would be handy.

    Sit down with a pencil and paper and draw the 'ideal' curve for your afternoon portrait. You might very well be able to make it.
    Using LPD or 130 instead of Dektol gives your paper greater range to hold these tones, and split filtering will be easy if you need to hold a longer scale.
    "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

  6. #15
    markbarendt's Avatar
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    Quote Originally Posted by df cardwell View Post
    There ARE limits. The film, for one thing. TMY & TX are great for this. TXP, not so good. Neopan 400, not good, for different reasons. FP4, great.
    Oh sure twist my arm and make me use TX, TMY, and FP4.

    Seriously though, the TXP info is a disappointment since TX isn't available in 4x5. I would have thought that this technique would have been more universal.

    What characteristics make a good film for this technique?



    Quote Originally Posted by df cardwell View Post
    You've got the idea perfectly, as well as live in a place where it would be handy.
    Yes it will. To that end I recently decided to start moving to shorter rolls, 12-20 shots, so that I will shoot an entire roll per subject/session and be able to develop more consistent negs.

    Quote Originally Posted by df cardwell View Post
    Sit down with a pencil and paper and draw the 'ideal' curve for your afternoon portrait. You might very well be able to make it.
    Using LPD or 130 instead of Dektol gives your paper greater range to hold these tones, and split filtering will be easy if you need to hold a longer scale.
    Already using LPD and the more I learn about it the better I like it.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  7. #16
    df cardwell's Avatar
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    What characteristics make a good film for this technique?

    A LOOOOOOOOOOOOONG Straight line, and a high Dmax.

    Foto Import published many film and developer combinations which should help you cut through the infinite combinations.

    I think this is a wonderful combination:



    Here is another:



    HP5 will be good, but I don't think you can do it with TXP. I've tried TXP in 220
    with dilute XTOL and minimal agitation, and got to an almost Normal curve,
    but it is almost all-toe and no shoulder, and your best friend on a soft, overcast day.
    "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

  8. #17
    2F/2F's Avatar
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    Good information. Thank you for posting it.

    I am interested to see the "unslid" curves laid on top of each other as well.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

  9. #18
    BetterSense's Avatar
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    ditto on the unslid curves. My brain is trying to translate them and rebelling.
    f/22 and be there.

  10. #19
    df cardwell's Avatar
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    "I am interested to see the "unslid" curves laid on top of each other as well."

    "ditto on the unslid curves. My brain is trying to translate them and rebelling"


    Well, guys, this is how I do it. Maybe you could get a pencil and paper... and draw it out for yourselves ?
    "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

  11. #20

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    thank you mr Cardwell...this is great info as I'm out in the "big" storm of 2010 here in NYC photographing in flat light with TMY2
    seems like these negs will get the rodinal treatment when I get home
    Thanks, Peter

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