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  1. #171
    markbarendt's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    I know the effects on the curve. I'm challenging the notion reduced exposure can provide better separations. To me it seems like if anything it would have the opposite effect since it shifts more of the exposure values into the part of the curve where compression is taking place.

    Regarding the sources of flare in testing etc, again, I'm refering mostly to flare caused by the subject/test target, not the lens. The kind of "veiling" lens flare Adams refers to is likely a relatively minor issue with most contemporary lenses.
    Regarding the separation: My impression is that flare works very much like pre-flashing, the greatest effect is on the lowest values. The more you pre-flash the flatter the toe gets. Less pre-flash/flare exposure as a result of less total exposure means a steeper toe.

    As to source, uhhh.
    Mark Barendt, Beaverton, OR

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

  2. #172
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    I know the effects on the curve. I'm challenging the notion reduced exposure can provide better separations. To me it seems like if anything it would have the opposite effect since it shifts more of the exposure values into the part of the curve where compression is taking place.
    Agreed.

    Regarding the sources of flare in testing etc, again, I'm refering mostly to flare caused by the subject/test target, not the lens. The kind of "veiling" lens flare Adams refers to is likely a relatively minor issue with most contemporary lenses.
    About 80% of flare originates with the subject, but it only exists when there's an optical system involved. There are a couple of different types of flare, veiling has to do with the optical system and camera creating an evenly distributed level of exposure. Another type is ghost which produces an image of the aperture.

    While flare plays a factor in the determination of film speed, for me it's more about the effect it has on the illuminance range. Kodak's contrast index for normal processing contains a value for flare. Their numbers won't work without it.
    Last edited by Stephen Benskin; 01-28-2013 at 01:46 PM. Click to view previous post history.

  3. #173

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    Quote Originally Posted by markbarendt View Post
    Regarding the separation: My impression is that flare works very much like pre-flashing, the greatest effect is on the lowest values. The more you pre-flash the flatter the toe gets. Less pre-flash/flare exposure as a result of less total exposure means a steeper toe.

    As to source, uhhh.
    Agree with the first part, but reducing the exposure doesn't change the amount of flare, or the shape of the curve. It just moves the entire exposure range further down the same curve so all other things being equal, underexposing is actually worse than doing nothing. It leads to more compression, particularly in the shadows.

  4. #174

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    Quote Originally Posted by AndreasT View Post
    Who is this Henry you guys are talking about? I couldn't find where he is first mentioned in this long thread.
    My guess is it's this guy Andreas:

    http://www.amazon.com/Controls-Black...ry+photography
    --
    Kenton Brede
    http://kentonbrede.com/

  5. #175

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    Quote Originally Posted by AndreasT View Post
    Who is this Henry you guys are talking about? I couldn't find where he is first mentioned in this long thread.
    Andreas - we're referring to Dr. Richard Henry. He was a clinical chemist, but also a photographer. As a scientist he was frustrated by how in magazines, books etc., photographers would present things about materials and technique as fact without any evidence, and often without even a reasonable basis.

    When he retired, he decided to equip himself with the appropriate tools and set about testing for the validity of many of the claims made by notable photographers, Zone System writers etc. He published the results in a book called Controls in Black and White Photography.

    While the materials he used are mostly outdated, perhaps the most important takeaway is that just because a well respected photographer says something about exposure, development, contrast, chemicals etc doesn't mean we should simply accept it as fact, especially in cases where no evidence, or a proper description of the experiment is given. And the description of the experimental method is very important. Even when presented with data (a characteristic curve for example), if we don't know how the test was done, it is often difficult to conclude anything.

  6. #176
    markbarendt's Avatar
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    I don't think that under exposing is being suggested, minimizing might be a better description, or maybe giving up the safety factors.

    Flare, like flashing, essential raises the lowest values significantly, easily doubling the density, without moving the highest values much at all, maybe 1%ish, you knew that though I'd bet.

    Flare, I theorize, like flashing needs to surpass a threshold point to have a significant effect. Less general exposure can help keep flare/flash exposure under the required threshold and therefore affect the image less.
    Mark Barendt, Beaverton, OR

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

  7. #177

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    I don't think it works that way with subject flare, where the high lumincances affect the lower ones. I think the characteristic curve under those conditions is basically a "given" (ie we cannot control the flare), and increasing or reducing exposure simply moves the subject range up and down that curve. So reducing the exposure would result in more compression because more of the subject values fall on the flattened portion of the curve.

  8. #178
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    Quote Originally Posted by Michael R 1974 View Post
    the most important takeaway is that just because a well respected photographer says something about exposure, development, contrast, chemicals etc doesn't mean we should simply accept it as fact, especially in cases where no evidence, or a proper description of the experiment is given. And the description of the experimental method is very important. Even when presented with data (a characteristic curve for example), if we don't know how the test was done, it is often difficult to conclude anything.
    Well put!

    One of the reasons why using the prefixes CI and ISO means the testing adhered to a methodology.
    Last edited by Stephen Benskin; 01-28-2013 at 03:17 PM. Click to view previous post history.

  9. #179
    Bill Burk's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    I don't think it works that way with subject flare, where the high lumincances affect the lower ones. I think the characteristic curve under those conditions is basically a "given" (ie we cannot control the flare), and increasing or reducing exposure simply moves the subject range up and down that curve. So reducing the exposure would result in more compression because more of the subject values fall on the flattened portion of the curve.
    Keep in mind that flare doesn't change the film's toe... it only affects the light falling on the film plane.

    This is an example situation where you can see "more clearly" what's happening because you separated your flare tests from your film tests.

    So the flare light provides enough light to lift you off the toe. There is compression, but it's compression of the light bringing you shadow tones to the film. Nothing you can do about that (except maybe a compendium hood) but try to keep the lowest of the shadow tones on the straight line portion of the film.

    But since flare lifted you up off the toe, you can still reduce your exposure and remain above the toe.

  10. #180
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    You guys are running away leaving me behind.
    What I gather rather expose more to reduce flair instead of decreasing exposure. Which I think is better anyway if the light permits.
    Otherwise if one decreases exposure one should extend development by an "X" amount to have a general compensation for the resulting flatness.
    You do some disagree?



 

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