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  1. #191

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    That's not the point I'm challenging though. I'm saying that reducing exposure under these conditions is detrimental.

    I think Stephen agreed with me earlier so I'l try to present this argument against reduced exposure again. I might be wrong but I don't think so. CPorter has said he's interested in practicality. I'm simply challenging the logic of something he's occasionally doing in practice under high subject flare conditions.

    Given a film, zero flare and fixed processing procedures, a characteristic curve is generated for the film. That is the curve under those conditions. It is independent of the exposure we decide to give. If we have a subject under these hypothetical conditions (say a grey scale), more exposure moves the subject up the curve. Less exposure moves the subject down the curve. But the curve does not change.

    Repeat this under a high flare scenario. The effect of subject flare is reduced contrast. The lowest negative densities are affected most. All other things being equal, compared with the zero flare curve, non-image forming light (ie flare) causes both an increase in density, and reduced contrast for exposure values below around Zone V. That is now the characteristic curve we have to work with. It is independent of the exposure we decide to give the film. As in the no-flare scenario, giving more exposure moves the subject (suppose it is the grey scale again) up the curve. Less exposure moves it down the curve. The shape of the curve doesn't change. So, if we reduce exposure, all we are doing is moving more of the subject into the lower part of the curve - where contrast is lower. It's not helping anything. It's just reducing local contrast for more of the subject values.

    I'm simplifying here, but perhaps the key point that's being lost is that the flare light that "lifts" the shadow values is non-image forming light.

    So I'll ask again - what is the purpose of giving less exposure? You might have a shorter print exposure time, but reduced local contrast in the shadow values in the negative - not a good thing from a Zone System perspective.

    So I actually disagree with the notion effective speed is increased by flare effects. Perhaps the speed "point" is increased, but local contrast in the shadows is decreased. If speed is a means to an end (ie sufficient local contrast in the shadows), we've lost more than we've gained, and this is compounded by reducing exposure.

    Andreas - you are not alone. I'm getting a little better at this (slowly) but I still often get lost in the various charts, diagrams etc. Stephen and Bill are much better at this than I am. I need to take a few days and slowly go through Stephen's stuff (not just this thread but several others).
    Last edited by Michael R 1974; 01-29-2013 at 07:40 AM. Click to view previous post history.

  2. #192
    AndreasT's Avatar
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    If flare / pre-exposure raises density more on the low density areas, then surely the density leat of the speed point would be raised more than the speed point resulting in less speed. No, Yes??

  3. #193
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    Quote Originally Posted by AndreasT View Post
    If flare / pre-exposure raises density more on the low density areas, then surely the density leat of the speed point would be raised more than the speed point resulting in less speed. No, Yes??
    No. Increased exposure in the shadow increases the shadow density and the speed point is reached with less exposure. This equals more speed.
    Last edited by Stephen Benskin; 01-29-2013 at 01:05 PM. Click to view previous post history.

  4. #194
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    Michael, I don't think it is actually less exposure in the shadows, especially with pre-exposure. It's pre-exposure + main exposure = normal shadow point. At the high end though total exposure can be lower.

    With flare there is only one exposure so I'm not sure how that gets any extra.
    Mark Barendt, Beaverton, OR

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

  5. #195
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    So I'll ask again - what is the purpose of giving less exposure? You might have a shorter print exposure time, but reduced local contrast in the shadow values in the negative - not a good thing from a Zone System perspective.
    Why not just print through any density created by excessive flare.

    So I actually disagree with the notion effective speed is increased by flare effects. Perhaps the speed "point" is increased, but local contrast in the shadows is decreased. If speed is a means to an end (ie sufficient local contrast in the shadows), we've lost more than we've gained, and this is compounded by reducing exposure.
    There's flare and there's excessive flare. All optical systems have flare. We just don't notice it unless it's excessive. Normal shooting conditions have normal flare and flare is part of normal film processing and part of film speed.

    Fun fact about flare and shadow compression. Ever wonder why Tri-X professional, with it's long toe, is considered a "studio" film? There's less flare with interiors and the ability to control lighting. In theory, regular Tri-X shot in daylight would have similar tonal distribution in the toe as Tri-X Pro shot in the studio.

  6. #196

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    Quote Originally Posted by markbarendt View Post
    Michael, I don't think it is actually less exposure in the shadows, especially with pre-exposure. It's pre-exposure + main exposure = normal shadow point. At the high end though total exposure can be lower.

    With flare there is only one exposure so I'm not sure how that gets any extra.
    CPorter indicated under these conditions he might give up to 2/3 stop less exposure (I assume this to mean 2/3 stop less exposure than he would otherwise give based on his meter readings and planned development). Pre-exposure + (normal main exposure less 2/3 stop). I'm saying if anything this will result in reduced local contrast through more of the subject range vs Pre-exposure + normal main exposure).

    I think we're all sort of on the same page regarding flare as pre-exposure. I'm just challenging the notion giving less exposure than one normally would, improves anything. If anything it puts more of the subject into the part of the curve that is compressed.

    I guess we'll just agree to disagree on this. I don't want to start pissing people off. The more people who participate in these threads the better.

  7. #197

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    Quote Originally Posted by Stephen Benskin View Post
    Why not just print through any density created by excessive flare.
    Exactly!


    Quote Originally Posted by Stephen Benskin View Post
    Fun fact about flare and shadow compression. Ever wonder why Tri-X professional, with it's long toe, is considered a "studio" film? There's less flare with interiors and the ability to control lighting. In theory, regular Tri-X shot in daylight would have similar tonal distribution in the toe as Tri-X Pro shot in the studio.
    Funny - In The Negative, Adams indeed says films with longer toes could be useful under low flare conditions. But all those years ago when I first got into his books this statement initially puzzled me because he doesn't really explain the effects of flare in the book.

  8. #198
    Bill Burk's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    I'm just challenging the notion giving less exposure than one normally would, improves anything. If anything it puts more of the subject into the part of the curve that is compressed.
    Now here is where I want to point out that you both can be right, and keep plugging away at what you like.

    Michael R 1974, I am in the camp where I don't change EI based on conditions. So for simplicity, I would NOT lower my exposure when faced with a scene that is buzzing with flare.

    CPorter, I totally support your idea to reduce exposure slightly in such a scene. Maybe you are holding your highlights off the shoulder? Maybe you see the shadows are badly compressed anyway so you aren't making things (much) worse than they already are.

    But after staring at this flare-included camera step wedge test family of curves (thanks Rafal Lukawiecki for the data), I think Michael R 1974 is right. You are well-advised to get up out of the very flat toe. I would keep Zone I above the little diamonds (0.1 speed point) or at least above the little 'c' marks (they happen to be what I used as Contrast Index measurement endpoints, meaningless on their own, especially meaningless because of the flare, but I have a hunch these little 'c' marks are a good place for Zone I exposures).




  9. #199
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    Quote Originally Posted by Michael R 1974 View Post
    I'm just challenging the notion giving less exposure than one normally would, improves anything. If anything it puts more of the subject into the part of the curve that is compressed.
    My scientific wild ass guess is that in a situation where there is a bunch of flare in a given shot for whatever reason, there is a sweet spot somewhere; but we are between a rock and a hard spot.

    On one side we have the toe that will compress important tones if we let placement fall too low, on the other when we add exposure excessive flare adds more and more generalized exposure that flattens the toe and reduces the the overall contrast of the image especially in the low tones.

    For me, given my metering and shooting techniques, I normally have enough latitude to reduce my exposure by a stop in almost any situation without losing important detail. In a high flare situation I could give that latitude away to get better overall contrast. I peg my shots to the middle somewhere and very much live by what Stephan expresses here.

    Quote Originally Posted by Stephen Benskin View Post
    Attachment 63292

    This shows the density ranges of negatives, that were judged to produce prints with excellent print quality, superimposed over the paper curve which they were printed on. Notice the diversity of NDRs. They all produced great prints. How precise does anyone actually have to be? Could this be the reason why good images are made regardless of the approach? The way I see it. Aim for the center. Even with all the potential variables and variances, you'll still hit the target.
    Your system may not have the same latitude. That's not a detriment, it just means that you may already be at the sweet spot I might move to, to minimize flare.
    Mark Barendt, Beaverton, OR

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

  10. #200
    AndreasT's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    No. Increased exposure in the shadow increases the shadow density and the speed point is reached with less exposure. This equals more speed.
    Sorry I have to get back to this, if the shadows are more flat beacause of a pre-exposure the rise in the film is more gentle and surely you would have to travel more down the curve to the right to reach the speed point.
    You have more density and theoretical speed increase over the unexposed film where there is no additional light.
    Now if you want soft shadows like mentioned before thats fine but if I want to keep the contrast in the shadows I would have to eventually expose more.



 

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