mcds

Discussion in 'Lighting' started by Ray Rogers, Nov 16, 2010.

  1. Ray Rogers

    Ray Rogers Member

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    Does anyone know offhand if mcds are a purely physical measurement...
    or, a psychophysical measurement?

    I think its the former but want to double check.

    Ray
     
  2. David Grenet

    David Grenet Member

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  3. Ray Rogers

    Ray Rogers Member

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    Thanks.

    Guess I'm a bit confused about how light meters work...
    are those readings also biased in favor of human vision?

    If you illuminate a subject in green light vs Blue or Red, is there an intentional bias in the meters logic?

    What is the purely non-psychophysical measurement of light for photographic purposes?
     
  4. ic-racer

    ic-racer Member

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    1⁄683 watt per steradian of green light is pretty much set in stone since 1979. It is a purely physical measurement.
     
  5. Ray Rogers

    Ray Rogers Member

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    Does that 1⁄683 watt per steradian apply to all wavelengths?
     
  6. Chan Tran

    Chan Tran Member

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    No. only visible light which is peaked in the green.
     
  7. Ray Rogers

    Ray Rogers Member

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    Ok, so the different wavelengths are weighted differently... in mcd;

    Jumping from mcd to photographic light meters, is this also true of light meters?

    or do they use a purely physical measurement?