BTZS - Do you make this adjustment?

Discussion in 'B&W: Film, Paper, Chemistry' started by Stephen Benskin, Sep 26, 2011.

  1. Stephen Benskin

    Stephen Benskin Member

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    I've read Phil Davis' Beyond the Zone System a number of times, but was struck the other week with something I don't remember ever reading. It's on page 95 of the fourth edition.

    "The amount of flare light that's present in the camera and its ultimate effect on the image are both unmeasurable. One thing is certain, though: There will be flare, and it will affect the image. At this point, we can only guess at the amount of adjustment necessary, so we'll assume a typical value and make the compensation by increasing the SI value by 10%

    For example, if your SI value is 0.9, multiply it by 1.1 (110%) to get 0.99, and add that to 0.06 (the IDmin value) to get 1.05. Then mark each curve at that level: 1.05 over B+F."


    My question to those who use BTZS is: Have you noticed this section and do you make this adjustment?
     
  2. pgomena

    pgomena Member

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    I measured the actual flare in my system and made a similar adjustment. I built a "black box" and photographed it in broad daylight. My view camera lenses averaged about 0.03 density units in flare, and my Canon 35mm lenses came up with 0.05 density units. I factored those into my system as described above.

    The "black box" was an 18" square box painted black on the inside and one face of the outside. The black face had a 4" hole cut in it, rim of the hole also painted black. I put a 3-sided black cardboard shade around the hole so sunlight could not strike the hole. Photograph the black face of the box in full daylight and measure the density of the hole. It will have some value above base + fog. That value is the flare in your system.

    Peter Gomena
     
  3. Stephen Benskin

    Stephen Benskin Member

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    Peter,

    When you did the black box test, did you fill the frame with box or not? And just to confirm, did you say you are adding the density range from the flare to the SI (NDR or LER) when you evaluate the curves?

    I did a black box test once. I did four separate shots of it with different toned cards surrounding the opening: black, white, grey, and checkered. I then made a sensitometric exposure. I've attached the results.
     

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