Basic exposure question???

Discussion in 'Exposure Discussion' started by gregmacc, Sep 2, 2009.

  1. gregmacc

    gregmacc Member

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    Help ... I'm confused. I've recently become interested in film after a long stint using digital processes. I've begun reading Henry Horenstein's "Beyond basic photography" but I can't seem to move past something he says on page 6 ... "An underexposed negative will not produce enough silver in the shadows to print adequate detail, so the shadows will print as flat, textureless, muddy-gray tones". By that I presume he means that the same shadows given more exposure and the same amount of development would print darker. The prints on page 9 would tend to support that idea. The T shirt in the underexposed print in the middle of the page is indeed a flat, muddy-gray. The same T shirt in the over exposed print to the right is a nice crisp black ... I don't get it ... Doesn't less exposure mean less silver density everywhere on the negative ... so darker tones everywhere on the print?
     
  2. Jeff Searust

    Jeff Searust Member

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    less silver on negative means darker on print--- I.E. a clear negative prints black. Shadows will be thinnest-- less silver

    and yes --less exposure prints darker.
     
  3. gregmacc

    gregmacc Member

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    Thanks Jeff ... So what's Henry on about?
     
  4. BobNewYork

    BobNewYork Member

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    You're right - less exposure and everything is darker; that is darker than it should be. Bright highlights will be darker than white or grey and, when it gets down to the shadows, they're likely to be pitch black with no detail in them.

    Hope this helps. When you first get into it it kinda makes your brain hurt !! But it really is worth persevering to give you a better understanding of the process - and make you a better craftsman and better photographer.

    Good luck.

    Bob H
     
  5. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    You may want to have more than one book to consult - they all have rather confusing back-arseward statements like HH's, above, and sometimes a second book can unconfuse the issue.

    If you underexpose then the negative will have shadows that are clear film with no detail and highlights will only get to a dim grey.

    If you then print this negatives, on a normal contrast grade of paper, so the highlights look correct then there won't be enough exposure for the shadows for them to get dark as they should be, and as the negative is underexposed there will be no detail so you just get grey splodges.

    However, if you now print this negative so the shadows are black, though without detail, the highlights will be a dingy grey as they don't have enough density in the negative to hold back enough light from the enlarger.

    If you have an underexposed negative you want to use a higher contrast grade when printing - that way you can get the blacks in the shadows and some lightness in the highlights.
     
  6. keithwms

    keithwms Member

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    The thickest portions of the neg become the highlights in print; the thinnest parts of the neg become the shadows. The difference in density is the contrast index.

    The important thing to remember is that the tone curve (neg density versus exposure) is nonlinear... it has a quite linear central part, but then it has a "knee" and at the other end a "toe." This nonlinearity is the source of your confusion, I suspect. If the tone curve were linear then tones would just shift proportionally when you under/over expose. But the nonlinearity affects the tone separation when you under/over expose. So under/over exposure has different effects on details falling on different parts of the tone curve.

    ~~~

    It is important to think a bit about what the slope of the tone curve means to how the tones will be rendered in print. Where the tone curve is very sloped, there will be more separation between adjacent tones. Where the tone curve is flatter (i.e. above the knee and below the toe) the tones will tend to clump up (=posterize). The latter situation is a major benefit of film (wrt/ digital) because there is a tendency for highlights not to blow in a specular way but rather to have a slow, smooth transition. What's so nice about film is how smoothly the tones ease into the knee and toe regions.

    Now, how you expose and how you develop will determine where the tones of your scene fall on the tone curve. People may tell you to rate the film at some number different from the box speed; sometimes that is because they prefer more shadow detail or more highlight detail... or similar effects. It's worthwhile to listen to those opinions, but first and foremost, you should learn how to get full range and optimal detail (=good tone separation) across the tones! And usually that means placing the centremost midtones smack dab in the middle of the tone curve and developing normally. Simple.

    You can also develop the film in such a way that there is less overall range or more overall range. You'd do this to build contrast or to reduce contrast.

    ~~~

    Short version:

    (1) In a well-exposed neg, the midtones will be somewhere around the middle of the tone curve;

    (2) If you overexpose, the resulting neg will be too thick and the highlights will tend to clump together at the knee of the tone curve;

    (3) if you underexpose, the resulting neg will be too thin and the shadows will tend to clump together at the toe of the tone curve.
     
  7. gregmacc

    gregmacc Member

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    Thanks Bob ... So if I'm right what is Henry saying? ... I've read further into the first chapter and everything else makes perfect sense. There must be something about the paragraph I quoted that I'm just not getting. I'm concerned that I'm missing something fundamental.
     
  8. gregmacc

    gregmacc Member

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    Sorry folks .. i posted the last thread (#7) before I saw the previous 2
     
  9. gregmacc

    gregmacc Member

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    Thanks Nicholas ... makes perfect sense ... and just as I would have explained it ... so it's not me?
    And yes, I am reading AA's "The Negative" at the same time ... though I do have some (other) issues with that one as well ... can you recommend any other books?
     
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  10. John Koehrer

    John Koehrer Subscriber

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    Some authors seem to write in a pretty convoluted manner. Sometimes it's a matter of finding the guy that writes the same way you read.
    I think I'd let the Adams series wait a while until there's some basic understanding, he gets pretty deep. IMO not especially a clear writer. The Ansel Adams Guides(2 volumes) are much easier.
    David Vestal's "The Craft of Photography" Charles Swedlunds "Photography". Phil Davis, Bruce Warren & a whole herd of others have all written the same information. Some are just easier to digest.
    I like the Vestal book which is old(60's-70's) He writes as though he were speaking to you. In plain English.
     
  11. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Vestal is a good writer, very forthright and plain. That was C.S. Lewis' advice - to write as you speak; he assumed you spoke well.

    Another of the golden oldies is Lootens on Enlarging and Print Quality.

    I would stay away from Minor White.
     
  12. RalphLambrecht

    RalphLambrecht Subscriber

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    Greg

    You are right and so is Henry, not a bad book by the way. The key here is that photographic processes are not linear. In other words, yes, less exposure means less exposure everywhere on the tonal scale, but 1/3 stop less is deadly for the shadow (information lost) but workable in the highlights (all info is there, just shifted). The old rule of photography is: 'expose for the shadows and develop for the highlights'. A lack of exposure shows its ugly face in the shadows first. That's what Henry meant.

    To prove his point to you, try this:

    1. expose a few frames with the same scene
    2. start with the box speed and then reduce the speed (increase exposure) by one stop at a time
    3. don't hesitate to overexpose by several stop (try 6 stops of overexposure)
    4. develop the entire roll as usual
    5. print all frames by keeping the print highlights consistent (you may have to change contrast slightly, and the exposure times will get ridiculous for the extreme overexposures, but ignore that for this test)
    6. when done , pick the frame with made the best print

    Dollars to donuts, it won't be the box speed. It will be a frame with amazing shadow detail at terrible film speed. Now, you got a new problem!
     
  13. Chan Tran

    Chan Tran Member

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    Thanks Ralph! I understand Henry completely and understand the frustration that Greg had but I didn't know how to explain it.
     
  14. RalphLambrecht

    RalphLambrecht Subscriber

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    Yeah, but you are better with math than I am. :smile:
     
  15. gregmacc

    gregmacc Member

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    Thanks for the responses all ... Might have a look at Vestal ...
    Ralph ... Better with math?
     
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  16. RalphLambrecht

    RalphLambrecht Subscriber

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    Was my comment not obviously directed at Chan Tran?