Shoulders, toes, knees and nose -- curves?

Discussion in 'B&W: Film, Paper, Chemistry' started by eric, Jun 13, 2005.

  1. eric

    eric Member

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    I'm techinically and graph challenged. I look at those film graphs and I don't know what they mean.

    But I'm willing learn. All I know, is that, when I use tri-x (35mm) and I develop d76/1:1 and shoot it a 200, great grain. Lovely tones. ***BUT***, when I have to print a neg with sunny highlights, I have a hard time printing the highlights. I love the negs on midtones.

    So does that translate to the shoulders or toes?

    When I process Delta 400 with PMK, I don't have a problem printing the highlights. What does that mean in relation to the shoulders?
     
  2. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    The low density part of the film curve where the shadows are is the toe, and the high density part of the curve where the highlights are is the shoulder.

    If you underexpose, then you are putting a wider range of tonal values on the toe, so you lose shadow detail, and you're probably not using a portion of the straight line portion of the curve between the highest density on the neg and the shoulder on the curve, unless the image has a particularly wide contrast range.

    If you overexpose or overdevelop, you are likely doing the same at the other end of the scale--putting the highlights too high on the curve with respect to the shadows for your print process and possibly putting them on the shoulder of the film curve, where all the highlights will appear to be about the same value and won't have good separation.

    With Tri-X it's easy to let the highlights get out of control. If it's happening all the time, then you're probably overdeveloping or over agitating.

    Delta 400 is much better at controlling highlights. If you're getting good highlight separation, then you're staying on the straight line portion of the curve (below the shoulder), and you're not overdeveloping, so contrast is staying within the range of the paper.

    Try Tri-X in PMK, since you're using it for Delta 400. It looks really nice, and you might find that the highlights are more moderated, particularly if you use VC paper.

    Delta 400 looks really good in Perceptol, if you haven't tried that.
     
  3. Donald Miller

    Donald Miller Member

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    The toe of the film characteristic curve is a portion of the curve in that the degree of incline is at a less extreme angle then the straight line portion of the curve. The toe is the region where the densities corresponding to the lower luminance values will reside...In other words the shadows. Since the slope is at a lower incline the shadow values are not as well separated as those on the straight line portion. On a film curve the toe will be at the lower left portion of the curve.

    The shoulder of the film's curve are where the highlight densities (depending on development) can exist. The shoulder is also a region that the incline of the slope diminishes from the straightline portion of the film and the highlights, if they reside on the shoulder, will be less well separated. If one develops excessively depending on film choice, the highlight values can actually be blocked because the adjacent tonalities are not separated to any remarkable degree. On a film curve the shoulder will be at the upper right of the curve.

    On paper these regions are reversed. The highlights will fall on the toe and the shadows will fall on the shoulder.
     
  4. eric

    eric Member

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    Very interesting! I'll have to maybe develop a little less. I use a cold light on my Beseler and I tend to process a tiny bit more...just in case type of thing.


    I tried that a couple of weeks ago and with 35mm, I didn't much like that grain. I *DO* like the grain with Delta 400 and PMK though. I think I have a bunch of Tri-X in 120 and I'll use PMK with that.

    Nope. Not yet. I'll check out my "Film Cookbook" and try it out.
     
  5. Claire Senft

    Claire Senft Member

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    In practical terms, forgetting charts and graphs, is that you are deeveloping too long for this type of lighting condition. Try 20% less.
     
  6. Will S

    Will S Member

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    Is there detail in the negative in the highlights? If so, then it should be printable, but you may have to use flashing or another technique to get it to work. Effectively you are moving the highlight parts of the curve into the straight line portion while keeping the shadows just about where they are.

    If there is some "there" there then you can print it.

    Best,

    Will