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  1. #391
    Photo Engineer's Avatar
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    When you are making huge batches and you are running continuously, and if you are rich enough to scrap a marginal batch, well then, things are nearly perfect. It appears as if things are not near perfect.

    Of course, this assumes that Marks process and data are spot on.

    PE

  2. #392

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    Quote Originally Posted by Photo Engineer View Post
    When you are making huge batches and you are running continuously, and if you are rich enough to scrap a marginal batch, well then, things are nearly perfect. It appears as if things are not near perfect.
    Of course, this assumes that Marks process and data are spot on.
    PE
    I re-checked my records. I developed a roll of Neopan 400 two days before the TMY2 rolls, and one day after. Both Neopan rolls came out fine. Here's the graph of the day-after Neopan roll:

    Click image for larger version. 

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    I've improved my methods to eliminate some wobbles in earlier graphs. Here's a graph of batch 0166 of TMY2:

    Click image for larger version. 

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    This one has wobbles, but you can see that it's roughly a straight line, unlike the latest TMY2 (batch 0167).
    What do you think of these graphs I've been posting lately? Do they look like what you'd expect?

    Mark Overton

  3. #393
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    Yes, they look OK to me.

    The sag in the middle of 0167 is a tipoff to me that there is a mismatch in speeds of the 2 emulsions. Of course, 166 and 167 may be cuts from the same or adjacent master rolls in the same batch and what we are seeing is the difference in handling due to outside factors, and the film may have passed the release test.

    PE

  4. #394

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    Quote Originally Posted by albada View Post
    Any idea why this occurs? Is this a well known phenomenon?

    Mark Overton
    You're testing with 35mm film, right? It would be interesting to compare with 4x5 sheet film.

  5. #395

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    Quote Originally Posted by albada View Post
    Converting 1.73 into stops: 1.73/0.3 = 5.75, which means that CI (at .58) assumes the scene contains 5.75 stops of luminance-range. Isn't that too low? I thought scenes contained a larger range than that, around 7 stops. It appears that CI is ignoring some of the highlights. Or did I miss something?

    Mark Overton
    Paging Dr. Benskin. Paging Dr. Benskin.

    OK, he must be off today...

    Think about lens flare and its effect on the luminance range. 7 stops in the real world will drop somewhat as the light goes through your lens on its way to the film.

  6. #396

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    Quote Originally Posted by Photo Engineer View Post
    Shifting curves (on 2 sheets of paper and over an illuminator)

    PE
    PE, do you still have your French curve, or did you like to freehand it? I miss French curves, and actually stencil templates in general.

  7. #397

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    Quote Originally Posted by Photo Engineer View Post
    When you are making huge batches and you are running continuously[…]
    PE
    PE, When pouring out 5000 ft of film, how much deviation was there from head to tail, and what was acceptable? Was EK able to get it pretty much the same for the whole roll?

  8. #398

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    Quote Originally Posted by Kirk Keyes View Post
    Paging Dr. Benskin. Paging Dr. Benskin.
    OK, he must be off today...
    Think about lens flare and its effect on the luminance range. 7 stops in the real world will drop somewhat as the light goes through your lens on its way to the film.
    Kirk, thanks for chiming in. Yes, I test with 35mm film. The Stouffer chart I got is intended for 4x5, forcing me to do some adapting. Do you think using sheet film would give different results?

    Hmmm, flare will push up the shadow-area, compressing the entire image a little, so I can see why 7 stops would become 6. So Kodak's 5.77 stops in its CI-ruler is close after all. Thanks for pointing that out.

    Mark

  9. #399

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    Knowing their cause allowed me to filter out the wobbles in the 0166 graph. Here's a comparison between Tmax-400 (TMY2) batches 0166 and 0167 developed identically in D316 (plus XTOL for comparison):

    Click image for larger version. 

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    What's interesting is that the slope of the upper half of 0167 is correct.

    Mark Overton

  10. #400
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    Quote Originally Posted by albada View Post
    Hmmm, flare will push up the shadow-area, compressing the entire image a little, so I can see why 7 stops would become 6. So Kodak's 5.77 stops in its CI-ruler is close after all. Thanks for pointing that out.
    I remember Stephen pointing out that a typical scene has 7⅓ stops, and a fixed flare model used by Kodak assumes a compression worth 1⅓ of a stop. I found this CI for LER Kodak chart, posted by Stephen, informative. It shows the CIs, after factoring the fixed flare, for various SBRs, and aim LERs. Nonetheless, I think Stephen prefers a variable flare model, where the amount of flare is proportional to the scene luminance range.
    Rafal Lukawiecki
    See rafal.net | Read rafal.net/articles



 

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