Adjusting contrast with R09

Discussion in 'B&W: Film, Paper, Chemistry' started by Lee Brown, Mar 19, 2012.

  1. Lee Brown

    Lee Brown Subscriber

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    Hi Guys.
    As a newbie at this whole darkroom thing, I was reading the Instructions for Fomadon R09 ( Link ) . It says the processing times are for Medium contrast g=0.65.
    I have two questions.
    1. What exactly does that mean ?
    and
    2. Does this mean I can get a higher or lower contrast by increasing/decreasing the times.
     
  2. markbarendt

    markbarendt Subscriber

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    Contrast rate is simply how fast you move from white to black.

    You adjust the rate to help control what and how things print.

    Starting off normal is good.
     
  3. mts

    mts Subscriber

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    g (gamma) is the slope of the straight-line portion of the density versus exposure curve. Gamma 1.0 and above is high contrast and the lower gamma values give more exposure latitude. To an extent you can achieve different gamma by varying process time, but developers perform best for a fairly small range of contrast values. More commonly one uses a different developer for higher contrast, as for example DK50 that was a favorite for "snappy" negatives destined for newspaper publication, or D19 for high contrast. D19 was most often used for scientific photography especially astrophotography where a good straight-line response was needed for quantitative densitometry. Ansel Adams often used D23 in divided development for lower contrast and to resolve shadow detail. D76 is the old favorite pictorial medium contrast developer from Kodak.

    Different films respond better or worse to certain developers, times, and dilutions. To determine your preference you should shoot a series of bracketed exposures of a typical scene, portrait, etc. and then process for different times and dilutions. Just shoot an entire roll (or several rolls) of film and then snip out test strips to process in different ways.
     
  4. MattKing

    MattKing Subscriber

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    In the order of your questions:

    1. As posted above, the contrast index is a measure of how the film transitions from detailed shadows to detailed highlights - a higher contrast index means a more abrupt transition from blacks, through greys to whites.
    2. Within a reasonable range, if you lengthen the developing time, you will increase the contrast.

    This link about assessing negatives may be informative: http://www.ephotozine.com/article/assessing-negatives-4682

    If you can, try some experiments. Shoot the same scene (in the same light) on a couple of short rolls, making sure they have sufficient exposure. Then develop them for different times to see what happens.
     
  5. Lee Brown

    Lee Brown Subscriber

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    Thanks everyone. The main reason I asked was because there was a thread about r09 a couple days ago where it was mentioned that in the past a much less dilute soup was used to develop to a higher density and contrast.
    By the way. Why exactly would that have been the case. Is it because the emulsions on the paper back then were better suited to a negative that had more contrast. Or was it more a fashionable or stylish thing to do at the time
     
  6. markbarendt

    markbarendt Subscriber

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    You can get high or low contrast with any dilution by adjusting with the other variables; time, temp, and agitation.

    All four variables affect the outcome. The overal contrast isn't the only thing that changes; grain, acutance, the shape of the curve are all adjusted.

    The reason I suggested starting normal is that for you to see what each of these variables does, it helps to have a baseline. Once the baseline is there then you adjust one variable at a time and see how that affects your system.

    Here's a link to start you with, http://www.apug.org/forums/forum216/69617-shaping-tone-curve-rodinal-negative.html

    The other thing to remember is that you are really after changes in the final result, the print. From camera to negative, and from negative to print, there are a bunch of variables that affect your outcomes too; those all need a baseline for you to understand what say changing dilution does and what you have to change to make that dilution change work.