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  1. #41
    Steve Smith's Avatar
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    Quote Originally Posted by Bill Burk View Post
    Using Weston rated speed of 80 for ISO100 I would get 1/130@f/18 which is EV15 and 1/3.
    If I set my meter to Weston 80 and point the dial at 400, I get f16 at 1/125.


    Steve.

  2. #42
    Bill Burk's Avatar
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    Quote Originally Posted by Steve Smith View Post
    If I set my meter to Weston 80 and point the dial at 400, I get f16 at 1/125.


    Steve.
    BINGO.

    There's a difference in the dials on Weston US and Weston Europe.

    If I set my Weston original, or my Weston II to Weston 80 and point the dial at 400, I get f16 at 1/150.

    If I set them to 64, I get f16 at 1/130. If I imagine nudging the dial slightly to the left of 400, I can imagine a reading of 1/125.

    So 381 is scientifically accurate, 400 is close. These should agree with Sunny 16. No chart required.

  3. #43

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    Quote Originally Posted by Bill Burk View Post
    BINGO.

    There's a difference in the dials on Weston US and Weston Europe.

    If I set my Weston original, or my Weston II to Weston 80 and point the dial at 400, I get f16 at 1/150.

    If I set them to 64, I get f16 at 1/130. If I imagine nudging the dial slightly to the left of 400, I can imagine a reading of 1/125.

    So 381 is scientifically accurate, 400 is close. These should agree with Sunny 16. No chart required.
    How do you get 381 for sunny 16?

  4. #44
    Bill Burk's Avatar
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    Quote Originally Posted by Chan Tran View Post
    How do you get 381 for sunny 16?
    Steve Smith worked it out in post #41

    400 is close enough

  5. #45

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    Oh I got it but the sunny 16 isn't EV15@ISO100. It stated that f/16 @ 1/ISO which is f/16@1/100 which is EV14 and 2/3.

  6. #46
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    Sunny 16 states that you use the closest shutter speed to 1/ISO. For ISO 100 this is 1/125.

    It seems odd that Weston would have two standards for their own sensitivity scale.


    Steve.

  7. #47

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    Quote Originally Posted by Steve Smith View Post
    Sunny 16 states that you use the closest shutter speed to 1/ISO. For ISO 100 this is 1/125.

    It seems odd that Weston would have two standards for their own sensitivity scale.


    Steve.
    But isn't 1/100 is closer and most cameras made in recent years have that shutter speed. Also your figure for 4095 cd/m^2 is for a meter calibrated with K=12.5 which is fine.

  8. #48
    Bill Burk's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Sunny 16 states that you use the closest shutter speed to 1/ISO. For ISO 100 this is 1/125.

    It seems odd that Weston would have two standards for their own sensitivity scale.


    Steve.
    Ah, well then we can easily talk about an ISO 125 film and be on the mark.

    It is odd that Weston would have two scales, but it coincides with the old confusing charts and our experiments.

  9. #49

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    Quote Originally Posted by Bill Burk View Post
    Ah, well then we can easily talk about an ISO 125 film and be on the mark.

    It is odd that Weston would have two scales, but it coincides with the old confusing charts and our experiments.
    Not really Bill. But OKay it's close enough.

    If we talking about ISO 125 film then the light level for EV15 is less than the 4096 Cd/m^2. The Sunny 16 light level should still be 3251 Cd/m^2.

  10. #50
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    Quote Originally Posted by Chan Tran View Post
    If we talking about ISO 125 film then the light level for EV15 is less than the 4096 Cd/m^2. The Sunny 16 light level should still be 3251 Cd/m^2.
    I usually treat ISO 125 film as if it is 100 anyway.

    And currently around here, it's dismal f5.6 rather than sunny 16.


    Steve.

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