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  1. #1
    David Lyga's Avatar
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    True or false: sunlight = sunlight

    Assume midday, with unrestricted sunlight. In neither case is the actual sun obscured by clouds. Now take these two scenarios:

    1) Scene fully lit under completely blue sky

    2) Scene fully lit under sky with many white clouds (but, again, sun, itself, is not obscured by clouds)

    Do the scenes require the SAME exposure or does the scene with the completely blue sky demand one stop more exposure? I think that the 'blue sky' scene does require more exposure because there is no benefit of the white clouds 'filling' in with more light. And, there are (British) photo books that attest to my assumption.

    Agree or refute: I do not bite. - David Lyga

  2. #2

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    I'd need a light meter and an appropriate day to contest that. Today it is cloudy, bleak, a little cold, and miserable out there. April 28, and hasn't felt like spring yet.

  3. #3
    Bill Burk's Avatar
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    Agree, the white clouds add fill light to scene 2.

    Not only because the entire scene may be "brighter"... but the illumination in the shadows themselves will be lifted by the clouds.

  4. #4

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    But a whole stop??

  5. #5
    Bill Burk's Avatar
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    Sure.

    Think of scene 1 as Sunny-16 and scene 2 like snow/sand... can be f/22

  6. #6
    David Lyga's Avatar
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    But, Bill, if we do not take shadows into consideration, I still maintain that the SUNLIT parts are brighter with the white clouds. And I am not the only one to believe that.

    Yes, HTF, a whole stop.

    This is a situation that is rarely discussed, but appropriately relevant. - David Lyga

  7. #7
    MattKing's Avatar
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    The shadows are critical when you are determining exposure of negative films.

    More diffusing and reflecting clouds means more light in the shadows.

    The suggestions that David refers to don't really apply to transparencies (or digital).
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  8. #8

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    I'd think that the clouds would fill the shadows a bit, making the total subject brightness range less. If you base your exposure on the shadows, then scenario 1, complete blue sky, would likely be more exposure and less development. The same scene with lots of white clouds filling in the shadows would be less exposure but likely a bit more development. I think I end up with N-1 in the first case a lot more than in the second, especially if I'm using any blue-subtracting filters.

    Best,

    Doremus

  9. #9
    David Lyga's Avatar
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    Roll film does not allow N-1 (unless the scenes are the same type). Thus, Ansel Adams does not come to the rescue here.

    Try to forget shadows here: we all know that fill light lightens them. I am talking about the SUNLIT portions of the scene and to simplify, let's focus upon ONLY a grey scale fully lit by sun. Would exposures in either case be identical or different. I think different. - David Lyga

  10. #10
    cliveh's Avatar
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    Quote Originally Posted by David Lyga View Post
    Assume midday, with unrestricted sunlight. In neither case is the actual sun obscured by clouds. Now take these two scenarios:

    1) Scene fully lit under completely blue sky

    2) Scene fully lit under sky with many white clouds (but, again, sun, itself, is not obscured by clouds)

    Do the scenes require the SAME exposure or does the scene with the completely blue sky demand one stop more exposure? I think that the 'blue sky' scene does require more exposure because there is no benefit of the white clouds 'filling' in with more light. And, there are (British) photo books that attest to my assumption.

    Agree or refute: I do not bite. - David Lyga
    For my money there would be no difference in exposure. In both cases (if I'm reading it correctly), the scene (that to be photographed) is lit by full sun, so if the surrounding illumination is blue sky or diffuse, it would have little influence over direct sunlight.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

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