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  1. #51
    Bill Burk's Avatar
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    You don't have the flare in the camera/flare quadrant yet.

    Though our normal subject has 2.20 range, the deepest shadows can't make it to the film as such deep shadows through the optics of the camera. There is a bit of light pollution, flare, that brings the lowest shadow up. (To the speed point? I don't know but it lifts it up.)

  2. #52
    Stephen Benskin's Avatar
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    Quote Originally Posted by Bill Burk View Post
    You don't have the flare in the camera/flare quadrant yet.
    You wouldn't be able to make this conclusion from the film curve alone. The log-H range would be the only information to work from.
    Last edited by Stephen Benskin; 05-13-2013 at 01:37 PM. Click to view previous post history.

  3. #53
    Bill Burk's Avatar
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    OK but flare is like light pollution for astronomers, it will keep you from ever being able to see the blackest black of the subject. I am guessing that flare was factored into the selected metered point.

  4. #54
    Stephen Benskin's Avatar
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    Quote Originally Posted by Bill Burk View Post
    OK but flare is like light pollution for astronomers, it will keep you from ever being able to see the blackest black of the subject. I am guessing that flare was factored into the selected metered point.
    Flare wasn't factored into that example. I wanted to show where the exposures fall in a no flare situation, that represents the same results as contacting, to illustrate how the shadows won't fall around the speed point if flare isn't incorporated. So, the next step is to add flare to the exposure equation.
    Last edited by Stephen Benskin; 05-13-2013 at 05:10 PM. Click to view previous post history.

  5. #55
    Bill Burk's Avatar
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    So, aside from flare, is there another missing detail?

  6. #56
    Stephen Benskin's Avatar
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    There are a few steps to determining the value of flare. The first step is to find the exposure for the shadow. This equation is the first equation in the upper left of the example. The example uses a subject luminance range of 2.20 logs with the diffused highlight starting at 100% reflectance. That means the shadow RD is 2.20. The next step is to determine the flare value. I’m using a flare factor of 2 or 1 stop. A one stop flare factor value of flare will equal the value of the shadow exposure. This value is then added to each calculated value of exposure.

    In the example, the actual nomenclature for Es and Ef should be Hs and Hf. I wanted to use separate symbols for the flare exposure in order to an attempt to minimize confusion.

    Click image for larger version. 

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    Flare has effectively doubled the shadow exposure at RD 2.20. It has gone from 0.0034 lxs to 0.0068 lxs with the addition of flare. This brings the shadow exposure up to the exposure for Hm. Without flare 0.0064 lxs would occur at an RD of 1.92 which is a touch under one stop difference.

    How does this look plotted?

    Click image for larger version. 

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    Matched to the film curve.

    Click image for larger version. 

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    And comparing the resulting negative densities from the no flare and flare examples.

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    Last edited by Stephen Benskin; 05-13-2013 at 09:30 PM. Click to view previous post history.

  7. #57
    Stephen Benskin's Avatar
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    Quote Originally Posted by Bill Burk View Post
    So, aside from flare, is there another missing detail?
    Do you have something in mind? Most of the other variables are part of the equation for q.
    Last edited by Stephen Benskin; 05-14-2013 at 12:11 AM. Click to view previous post history.

  8. #58
    Stephen Benskin's Avatar
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    Letís look at an exposure example relating the numerical values for exposure with Zone System designations. Because the Zone System keys the luminance range to the exposure meter, the highlight luminance is a touch less than 100% reflectance. In fact, every reference point is shifted by a RD of 0.02. Not that this is a big deal, it just makes comparison between the two example more difficult. Iíve added a 18% reflectance guideline.

    Because this is a no flare model, the exposures will be identical to sensitometric exposures. In camera Zone System testing, while using an optical system, produces minimal to effectively zero measurable flare. So, this example can be thought of as a close representation of Zone System in camera testing.

    Click image for larger version. 

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    We can see that the metered exposure is correct for a 125 speed film, and 1.0 logs below is the speed point and the exposure there will produce a film speed of 125. Like with the 2.20 luminance range example, the shadow exposure falls below the speed point.

    From the flare example, we know that the shadow will be brought up to around the speed point under normal shooting conditions, but this isn't factored in with in camera Zone System testing. The idea with ZS testing is to align the exposure Δ 1.20 logs below the metered exposure point with the speed point which is Δ 1.0 logs below the metered exposure. This usually means increasing the camera exposure (under rating the film).

    The next example shows an exposure increase of 2/3 stop. This brings the shadow exposure up to the speed point. It also raises up the metered exposure and where it will fall. Instead of being at 0.064 lxs, it is at 0.102 lxs. This means the EI setting on the camera for a 125 speed film will be at 8 / 0.102 or EI 78 (80). If some experimental error exists, the EI could easily be 64 or half the film speed.

    Click image for larger version. 

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    Notice how the negative density range in the adjusted exposure example is at the traditional Zone System 1.25. This is what one would expect from a sensitometrically exposed 2.10 exposure range, but not from a 2.10 subject luminance range shot through an optical system incorporating flare. One way to tell the target 1.25 negative density range isnít appropriate is to check to see how it fits with the photographic paper.

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    The paper LER that is considered to be in the middle of the range for grade 2 paper printed with a diffusion enlarger is 1.05. The LER is determined between the points 0.04 over Pb+f and 90% of the paper Dmax. Clearly the 1.25 negative density range doesnít fit a grade 2 paper. But many Zone System practitioners swear that they use something close to 1.25 for their testing range and their negatives fit well on a grade two paper. The reason for this is the 1.25 negative density range comes from a no flare test and the prints are from negatives made in a camera with flare which reduces the negative density range.
    Last edited by Stephen Benskin; 05-14-2013 at 10:49 PM. Click to view previous post history.

  9. #59
    Bill Burk's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    The paper LER that is considered to be in the middle of the range for grade 2 paper printed with a diffusion enlarger is 1.05. The LER is determined between the points 0.04 over Pb+f and 90% of the paper Dmax. Clearly the 1.25 negative density range doesnít fit a grade 2 paper. But many Zone System practitioners swear that they use something close to 1.25 for their testing range and their negatives fit well on a grade two paper. The reason for this is the 1.25 negative density range comes from a no flare test and the prints are from negatives made in a camera with flare which reduces the negative density range.
    1.05 is my aim. I don't quite understand where the traditional 1.25 came from but I have heard many practitioners choose that. Your explanation makes sense.

  10. #60
    Stephen Benskin's Avatar
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    Quote Originally Posted by Bill Burk View Post
    1.05 is my aim. I don't quite understand where the traditional 1.25 came from but I have heard many practitioners choose that. Your explanation makes sense.
    Adams, The Negative, page 220.

    Good to know someone is following this.
    Last edited by Stephen Benskin; 05-15-2013 at 09:50 AM. Click to view previous post history.

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