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  1. #11
    Stephen Benskin's Avatar
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    The first example didn't use the reciprocal of the anitlog. You only used the anitlog.

  2. #12

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    Whoa!!!

    I think I must have read Stephen's post (#4) incorrectly and put the brackets in the wrong place or something? Is this formula correct or not:

    H= 1/10^D * I

    H = I / 10^D

    or is it

    H = 10^D * I

    Sorry about this, guys.

  3. #13
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Whoa!!!

    I think I must have read Stephen's post (#4) incorrectly and put the brackets in the wrong place or something? Is this formula correct or not:

    H= 1/10^D * I

    H = I / 10^D

    or is it

    H = 10^D * I

    Sorry about this, guys.

    H= 1/10^D * I

  4. #14

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    What the heck is going on here?

    H = 0.08

    1/10^0.3 = 0.5

    0.08 = 0.5 * I

    I = 0.08 / 0.5

    I = 0.16

    This can't be. I'm losing my mind.

  5. #15
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    Quote Originally Posted by Michael R 1974 View Post
    What the heck is going on here?

    H = 0.08

    1/10^0.3 = 0.5

    0.08 = 0.5 * I

    I = 0.08 / 0.5

    I = 0.16

    This can't be. I'm losing my mind.
    H = 0.08 * 0.5 = 0.04

  6. #16

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    So my first substitution was wrong (H=0.08). I wasn't using the equation properly.

    Need to rethink this.

    I'm not understanding what this formula does. H is exposure in lux-s. Then on the right side of the equation we have I in lux, and then the other term which is the reciprocal anti-log of D. Somehow multiplying I (lux) by the reciprocal anti-log of D gets us to lux-s? How?
    Last edited by Michael R 1974; 05-27-2013 at 07:10 PM. Click to view previous post history.

  7. #17
    Stephen Benskin's Avatar
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    Both are in lux sec. Don't over think it. Light falling on the step tablet, the density of the step tablet, and light that passed through.

    Use this for a reference.

    Click image for larger version. 

Name:	Sensitometric exposure for 125 speed.jpg 
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    Last edited by Stephen Benskin; 05-27-2013 at 07:26 PM. Click to view previous post history.

  8. #18

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    Apologies I was thinking of I as intensity, not illuminance. Amazing

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