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  1. #51
    markbarendt's Avatar
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    No sweat Michael. Google can't find much either.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #52
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    Quote Originally Posted by PeterB View Post
    Hi folks,

    I was rather annoyed at myself to discover that I over exposed a 120 roll of HP5+ by a whopping 4 stops ! The good news is that I think my highlights will not be compressed at all but I wanted to run my solution past you.

    The SBR was 7 stops from Zone II to VIII inclusive which would have otherwise lead to Normal (N) development time. In short I plan on reducing the film development time to be that for N-1 which in my process will lower the gamma from 0.5 to 0.4

    Below you can see my analysis, but I am amazed that I can still keep my scene in the straight line portion of the curve by forcing a minor reduction to its CI/gamma/slope. I will just print using 1 grade harder MG filter. What am I going to lose out on here ? This seems too easy to recover from.

    ** warning that a bit more theory and maths will now follow... **

    I have analysed the HD/characteristic curve of HP5+ and it is linear out to at least a density of 2.1 log units which has basically been my saving grace here. Normally a neg exposed for N development in my process would result in a density ranging between 0.3 and 1.35 on the neg. [gamma=(1.35-0.3)/(7x0.3)=0.5]. 1.35 is nowhere near 2.1 but 4 stops over exposing would put the density right on 2.1, however if I reduce the gamma to 0.4 and calculate the range for Zone II to IX, you will see it comfortably makes it in. I am calculating from zone II up to Zone IX (i.e. an 8 stop range) as I want to include even the last nuance of detail in my highlights. So here is the formula:

    Gamma=0.4=(D_zone_IX_end - D_zone_II_start)/((4+8)x0.3)
    0.4=(D_zone_IX_end - 0.3)/((4+8)x0.3)
    D_zone_IX_end = 1.74.


    Now because D_zone_IX_end<2.1 , I should be OK. In fact because I still have a bit of wiggle room I could develop to N-0.5 which would give D_zone_IX_end = 1.92 Developing for N would put D_zone_IX_end right at a density of 2.1 and permit no room for any error in dev time/temperature/age/minor film exposure variations etc.


    regards
    Peter
    Forgive me for being devil’s advocate here, but if you are over exposing by 4 stops, isn't the rest of your post irrelevant, as you should concentrate on exposing correctly.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  3. #53
    markbarendt's Avatar
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    Quote Originally Posted by cliveh View Post
    Forgive me for being devil’s advocate here, but if you are over exposing by 4 stops, isn't the rest of your post irrelevant, as you should concentrate on exposing correctly.
    Oh Clive. You're so silly.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #54

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    I sincerely hope the silliness of cliveh's posts is intentional.

  5. #55
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    Quote Originally Posted by Michael R 1974 View Post
    I sincerely hope the silliness of cliveh's posts is intentional.
    Probably not, but perhaps I'm misreading the original post. Perhaps you can please explain.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  6. #56
    markbarendt's Avatar
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    Quote Originally Posted by cliveh View Post
    Probably not, but perhaps I'm misreading the original post. Perhaps you can please explain.
    Have you ever screwed up something important, figured it out too late, and not known how to fix it?
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  7. #57
    cliveh's Avatar
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    Quote Originally Posted by markbarendt View Post
    Have you ever screwed up something important
    Yes, but have tried not to repeat it.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  8. #58
    markbarendt's Avatar
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    Quote Originally Posted by cliveh View Post
    Yes, but have tried not to repeat it.
    I think Peter will endeavor not to repeat his mistake too and he learned things he didn't know and has new questions to answer.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #59
    cliveh's Avatar
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    Quote Originally Posted by markbarendt View Post
    I think Peter will endeavor not to repeat his mistake too and he learned things he didn't know and has new questions to answer.
    So why is it silly to highlight the cause rather than the effect?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  10. #60
    markbarendt's Avatar
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    One thing that I thought about bringing up earlier but forgot to was that what Peter did by accident is something that Kodak, Fuji, and Ilford have been encouraging for many, many years on an industrial scale.

    http://ilfordphoto.com/products/prod...ILFORD+CAMERAS
    http://www.kodak.com/ek/US/en/Single_Use_Cameras.htm
    http://www.fujifilm.com/products/film_camera/quicksnap/

    The latitude of the film is what makes single use cameras workable.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin



 

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