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  1. #1
    Bruce Osgood's Avatar
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    SBR & Development Adjustment

    When considering an adjustment to development of negatives, one thing we seem to consider is the Shadow to Brightness Range. I thought this was like a spot metered Shadow EV of 6 subtracted from a Bright EV of 13 giving a SBR of 7 stops. From that 7 we would make a personal discission whether or not to adjust our development time and by how much. Perhaps the 7 is a lot, perhaps a little or perhaps no adjustment is needed.

    It dawned on me that this may be the wrong way to approach the question of +/- development. If we believe in the tenant of "Exposure places the shadows and development places the highlights", then shouldn't we consider adjustment to the highlight portion of the spectrum because the shadow portion is not going to be altered regardless? In the example of EV's 6 and 13 suppose the mid-gray were 11 EV, wouldn't a better conclusion be that you had 2 stops to consider?

    I think this would be important in low key photos where you have an image of long toe and short straight line.

    Perhaps you see no merit in the question but these kind of things bug the heck out of me.

  2. #2

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    BTZS

    If you get a copy of Phil Davi's BTZS it will tell you how to test both your paper and film.

  3. #3
    mikepry's Avatar
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    Also, I might add, that BTZS.org is much better suited for these types of questions and learning the BTZS approach. Try this link.............

    btzs.org
    "EVERY film and paper is good .......... for something"
    Phil Davis

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    Bruce,
    The shadow ev 6 subtracted from the highlight ev 13 gives you 7 which is added to 5. So the SBR is 12. A SBR of 7 is considered normal.

  5. #5
    Bruce Osgood's Avatar
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    Thank you

    Claire
    mikepry
    wn blunt

    Your replies are useful and I will dig further.

  6. #6
    noseoil's Avatar
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    High SBR

    Bruce, this is one of the first shots with a high contrast range (shot was 7 2/3 on the bottom and 15 2/3 on the top) I attempted as a sort of test of BTZS concepts. I exposed at ev 9 to make sure shadows had enough density and then backed down development to bring in highlights. As Mike and others have mentioned, BTZS was the only way I could understand this extreme range of values and translate it into a print which worked. While not a great image, it does give an idea of how BTZS values are applied in terms of a real shot.

    While Phil Davis's book gets a bit long on numbers, the concepts expressed in his work are the only way I can see to relate paper, film, exposure, development and printing in this type of extreme situation. All the other systems fall apart in a scene with this type of exposure and development issues. Try it, you'll like it. tim

  7. #7
    mikepry's Avatar
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    Tim...are you showing off?????? Seriously, that is unbelievable what you have attained with that image. We are expecting to see some nice cactus blooms in the very near future with all the good rain you have had out there.
    "EVERY film and paper is good .......... for something"
    Phil Davis

  8. #8
    Zathras's Avatar
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    Quote Originally Posted by wm blunt
    Bruce,
    The shadow ev 6 subtracted from the highlight ev 13 gives you 7 which is added to 5. So the SBR is 12. A SBR of 7 is considered normal.
    [FONT=Times New Roman][SIZE=2][COLOR=RoyalBlue]Wouldn't that depend on how Bruce is metering? If he's using the Incident Method, this would be correct. If he is metering with reflected light, and if my understanding of BTZS is correct, subtracting 6 from 13 would make for a 7 stop SBR. I am just starting down the slippery slope of BTZS myself, so I realise that I may be wrong. It wouldn't be the first time... [/COLOR] [/SIZE] [/FONT] :rolleyes:

    Mike Sullivan
    When the chips are down,

    The buffalo is empty!!!



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    Mike,
    You can use a spot meter with the BTZS system instead of incident meter and it works just fine. I use both but when possible I use the incident.

  10. #10
    Bruce Osgood's Avatar
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    My origional Post:
    "I thought this was like a spot metered Shadow EV of 6 subtracted from a Bright EV of 13 giving a SBR of 7 stops. From that 7 we would make a personal discission whether or not to adjust our development time and by how much. "


    Quote Originally Posted by Zathras
    [FONT=Times New Roman][SIZE=2][COLOR=RoyalBlue]Wouldn't that depend on how Bruce is metering? If he's using the Incident Method, this would be correct. If he is metering with reflected light, and if my understanding of BTZS is correct, subtracting 6 from 13 would make for a 7 stop SBR. I am just starting down the slippery slope of BTZS myself, so I realise that I may be wrong. It wouldn't be the first time... [/COLOR] [/SIZE] [/FONT] :rolleyes:

    Mike Sullivan

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