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  1. #11
    kintatsu's Avatar
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    I would imagine that the same amount of light would be falling on both, as they are directly lit by the sun. Giving panchromatic b emulsion as the film, the exposure should stay the same, perhaps up to 1/3 less. That is entirely without taking into account the actual values.

    I have found that in similar cases, the sunlit values don't change much. It's when filters and other values within the scene are accounted for, there can be quite a difference.

  2. #12

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    Not to sidetrack the discussion--but I always wondered how NASA pre-planned exposure for the astronauts. The sky on the moon was black. Did they use Sunny f/16?

  3. #13
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    When I incident meter(loosly BTZS for roll film) I may prefer to have scene 2 every where.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.

  4. #14
    David Lyga's Avatar
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    It is admittedly difficult to test this definitively: one would have to wait days on end for the perfect situation. I think that the masterful Focal Encyclopedia of Photography parses this issue though and agrees with what I have inferred.

    Like others here, I originally thought that an 'elegant' answer such as 'it is still lit by the same light' would trump all because of the logic that it seems to rest upon, but there really might be a difference. We'll wait for more replies to this simple but confusing quandary.

    I will not be at another computer until Monday. - David Lyga

  5. #15
    Bill Burk's Avatar
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    Quote Originally Posted by HTF III View Post
    Not to sidetrack the discussion--but I always wondered how NASA pre-planned exposure for the astronauts. The sky on the moon was black. Did they use Sunny f/16?
    They followed instructions like these...

    http://www.apug.org/forums/showthrea...ferrerid=38808

  6. #16
    Bill Burk's Avatar
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    Quote Originally Posted by David Lyga View Post
    It is admittedly difficult to test this definitively: one would have to wait days on end for the perfect situation.
    We wait days on end for this situation anyway... Beautiful light.

  7. #17

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    Thanks Bill. I mean on the moon in 1969. EVERYTHING was a chance and a risk then. Can you imagine the wonder and worry in the minds of all the NASA people then? I'm betting they used Sunny f/16 on the side of the LEM facing the sun. How could they really know?

  8. #18

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    Agree or refute: I do not bite. - David Lyga
    @ David. Agree. But definitely by not one full stop. That (1 full stop) would be the case if the clouds had only forward scattering; then they would distribute on the ground a flux equal to the incoming solar flux. But as we know from air travel, clouds also reflect a lot of sunlight towards deep space. Which can be confirmed without flying: under a cloud cover the light flux is less than under direct sun. Closer to 1/4 (2 stops from sunny 16). So, in the most favorable case (under a small clear hole in a sky otherwise covered with nice white cumulus) one might hope for 1+1/4=1.25=+1/3stop; rough, quick estimate.

    @ other readers. If you don't agree, I won't go into one of those sterile forum controversies; just use your light meter under comparable conditions (same period of year + same daytime = same sun elevation).

    Measurement worth thousand theories. Confucius. (or, was it Galileo? or Groucho?)

  9. #19

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    In the last analysis I think it varies from scene to scene. Certainly cloud cover can reflect light---city skyglow on a cloudy night will attest to that---but there are so many variables that I would be greatly surprised to find a usable general rule (other than "when in doubt, meter").

    -NT
    Nathan Tenny
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    The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
    -The Little Technical Library, _Developing, Printing, And Enlarging_

  10. #20
    Bill Burk's Avatar
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    Yesterday, out on the dressage court with my sister-in-law Patience, I was a stop over Sunny-16. No clouds. This was light sand, so reflecting up to the subject.

    Same light, different scene, the ranch house, no sand. I felt that the shaded side of the building had to be at least Zone IV, so I gave more exposure. The white pickup truck in full sun will be a challenge to print.

    Will have to wait until the clouds come out to test bernard_L's theory. For now, it's a sunny day with blue skies...
    Last edited by Bill Burk; 04-28-2013 at 02:49 PM. Click to view previous post history. Reason: senseless name-dropping, better to keep it real

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