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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.
    Attached Thumbnails Attached Thumbnails Rodinal-agitation-study.jpg  
    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. #2
    Thomas Bertilsson's Avatar
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    Proof is in the pudding. Don, among others, has helped me very much with my film processing, getting it under control by re-learning basics and eliminating fancy work. By learning how to adjust agitation to exposure and lighting conditions, I have effectively opened up a whole new spectrum of possibility, and the cool part is - it's with the same materials every time!
    I have used Kodak TMY-2 for a good while now, and while cost has forced me to use some cheapo Arista film now and then, the TMY-2 is my mainstay. Replenished Xtol is my developer of choice, and by exposing the film from EI 200 to 800, and subsequently altering development time and agitation intervals from 1m all the way to 5m I have learned how to control what my prints are going to look like.
    This works, ladies and gentlemen, and I proved it to myself by doing it; with great guidance.
    "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

  3. #3
    Jerevan's Avatar
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    Thanks, df! I was thinking of this the other day, wondering when you were going to write an article on Rodinal.

    I see that you have witheld the speed rating of the film, but I assume that getting box speed out of Rodinal is like trying to have the cake and eat it. My observation with Rodinal (and its cousins such as R09) is that I seem to get good highlights but seldom any decent shadows, even when downrating from the box speed.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  4. #4
    df cardwell's Avatar
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    Jerevan: One way to look at the red curve is the shadows were 'pushed' and the highlights were 'pulled'.
    Try that development time, and bracket the exposure from 100 to 1600.

    Then let us know !
    "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

  5. #5
    Jerevan's Avatar
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    Yes, I will try it out and see what I'll get. Should be interesting.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  6. #6
    juan's Avatar
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    Interesting - I think back to Fred Picker advocating basing exposure on Zone VI rather than II or III.
    juan

  7. #7
    df cardwell's Avatar
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    And it was talked about in The New Zone System Manual; White, Zakia, and Lorenz; 1977 or 78
    Well worth reading.
    Last edited by df cardwell; 12-17-2009 at 03:55 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

  8. #8
    Ian Grant's Avatar
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    Interesting, the conventional wisdom in the 80's and 90's (in the UK) was that the best way to alter the curve with Rodinal was by altering it's dilution, and that works extremely well.

    Peter Goldfield was the Guru of Rodinal, the quality of his 35mm Agfapan negatives and prints was stunning, many wouldn't believe he'd shot them with a Leica and not medium format. Peter had gone on workshops with Paul Hill before spending some time with Paul Caponigro in New Mexico, he imported Agfa materials into teh UK, rebuilding their market, and was a staunch supporter of the workshop system.

    So there's another approach which is fairly unique amongst developers for controlling the curve. I used 3 different dilutions for N+2, N and N-2 development which gave far more control than simply altering development time or agitation.

    Ian

  9. #9
    Lee L's Avatar
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    Quote Originally Posted by Ian Grant View Post
    ... So there's another approach which is fairly unique amongst developers for controlling the curve. I used 3 different dilutions for N+2, N and N-2 development which gave far more control than simply altering development time or agitation.

    Ian
    Arnold Gassan published his system for contrast control through dilution with HC-110 in the 70's. It's been discussed several times here on APUG. Perhaps you could post a separate 'How To' with specifics on Goldfield's and your dilution/contrast techniques with Rodinal.

    Lee

  10. #10
    df cardwell's Avatar
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    Ian: Good stuff. Peter left us far too soon.

    Technique doesn't conflict with itself. Curve shaping by dilution has been the preferred way for most sophisticated photographers since the mid '60s. It has its limits, however, and by considering the use of time and agitation, we multiply the potential of the technique.

    Increasing the speed of the toe is always related to the time spent in the developer. It defies the way we have come to think about film, however, for we are pretty well indoctrinated to the"dog wagging his tail" image of a curve family. BUT if we allow ourselves to think of a different model, we open ourselves up to perceiving new ways to build negatives. See: Lorenz. New Zone System Manual.

    The familiar notation of exposure and development is, of course, N-2, N, and N+2. Small adjustments are needed to maintain the Zone I or Zone II densities, while development alone raises and lowers the Zone VIII.

    Lorenz suggested a simultaneous adjustment: Exp +2/N-2; Exp -2/N+2. This allows the midtone to maintain its density, while Zone II and Zone VIII are adjusted. If the Exposure Index is taken from Zone V, or Zone VI, then the speed of the film is constant while the scale is expanded or contracted.

    Adding the tone curve shaping is a useful refinement to the process. I use 1 film for all my work, TMY2.
    Using agitation and time (and, yes, dilution) I have 3 developments to choose from, a 10 step scale, and 8 step scale, and a 12 step scale. The important thing for me is that the the palettes have the same Exposure Index. So, I only need to make an incident reading, and begin shooting. Development can be decided beforehand or afterward, to satisfy either emotional or technical requirements of the image.

    For instance, if the light is good, but there are unavoidable bright highlights on the face, I use an XTOL curve (second graph below) whose shoulder compresses the bright highlights.

    If the light is normal, which for me is slightly flat and soft, with no direct light on the faces, I use the 10 tone, normal curve; Edwal 12.

    If the light is completely overcast and flat, I use Rodinal to build an 8 tone scale.

    By using this method of tone curve shaping, I was able to maintain an EI of 400 while devising 3 suitable tone curves. It has been a reliable method for me, letting me make quick decision while photographing people. It works equally well for 4x5 and 35 mm, because there is only one film.

    Rodinal is the focus of this conversation, but XTOL, Pyrocat, Edwal 12 and other developers work well, too. For portraiture, I use 3 development schemes, and 3 different developers to make 3 coordinated palettes.

    We've now gone beyond the planned scope of this article, but Ian brought an excellent point.

    .
    Attached Thumbnails Attached Thumbnails Zone-Models.jpg   3-tone-curve-palettes.jpg  
    Last edited by df cardwell; 12-18-2009 at 08:15 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

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