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  1. #31
    Stephen Benskin's Avatar
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    When I was working in the photo lab industry back in the day, I had access to Dick Dickerson. He was the head of the B&W R&D department. I even spent the day with him and the head of the team that created the T-Max films and Xtol. They are the ones that told me the story about D-76 being the primary developer during the R&D of the T-Max films.

  2. #32
    Rudeofus's Avatar
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    From what I read here on APUG, all films to be released were tested for satisfactory results with D-76, because that was/is the most commonly used developer. "Full speed" is a property of an emulsion and a hard limit, therefore D-76 can't possibly give "full speed" if Microphen, TMAX, DD-X and Xtol give 1/2 - 2/3 stop more. As it just so happens, if you add 2/3 stop to ISO 250, you end up very close to ISO 400 ...
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #33

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    I'm not following. When you say "full speed", it sounds like you are defining it as "maximum emulsion speed", which is not implied by the ISO standards. There is likely a hard limit to maximum speed for a given emulsion (and of course we would need to define it), but for TMax 100 (just an arbitrary example), that might be considerably higher than its nominal or ISO speed.

    I assume when Kodak says D-76 yields full emulsion speed with a film - say TMax 100, that they mean you can get 100. And that other developers such as Microphen, XTOL etc. might give you slightly higher speeds.

  4. #34
    Stephen Benskin's Avatar
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    Let's not forget that most people compare the ISO to the results from Zone System testing and the two testing methods aren't comparable. All things being equal, the Zone System test will almost universally yield a 1/2 to 1 stop slow EI than the ISO speed. This doesn't mean that the ISO speed is wrong. It means the test parameters are different.

  5. #35
    Rudeofus's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    I'm not following. When you say "full speed", it sounds like you are defining it as "maximum emulsion speed", which is not implied by the ISO standards. There is likely a hard limit to maximum speed for a given emulsion (and of course we would need to define it), but for TMax 100 (just an arbitrary example), that might be considerably higher than its nominal or ISO speed.
    A well formulated developer will give you "full emulsion speed". There are some special developers which yield a concave characteristic curve, and as a result can gain a tiny bit more shadow detail without letting contrast go through the roof, but the wiggle room is small. "Full emulsion speed" seems to refer to the maximum speed you can get with a good developer that gives a straight characteristic curve. Both D-76 and TMAX have such a straight characteristic curve, and if TMAX gives you 2/3 stops more than D-76, the latter can't possibly give you "full speed". Bill Burk's measurements seem to confirm this.

    Quote Originally Posted by Michael R 1974 View Post
    I assume when Kodak says D-76 yields full emulsion speed with a film - say TMax 100, that they mean you can get 100. And that other developers such as Microphen, XTOL etc. might give you slightly higher speeds.
    The question is: when did Kodak state that? Did they make that statement before TMAX/Microphen/DD-X hit the market? Did they make that statement when the ISO speed definition mandated a specific developer?

    In my opinion the term "full speed" would be meaningless if many developers can reach more.
    Trying to be the best of whatever I am, even if what I am is no good.

  6. #36

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    It could be a semantics issue I get what you're saying. "Full emulsion speed" isn't a very clear phrase. The way I always read it is to mean the nominal (maybe "native" is a better term) speed of the film (which is still not clear). But since D-76 has been Kodak's release developer for as far back as probably matters, when they call it a "full emulsion speed" developer I assume it to deliver box speed by ISO standards, and that this would have been the case even when ISO speeds were determined using specific mandated formulas (ie D-76 would match it).

    Crawley would tend to lean more in your direction, since he "felt" the true inherent speeds of films were higher than people were all used to at the time. This seems to be based mostly on the fact he was big into Phenidone, which tended to give small increases in properly balanced formulas, vs comparable MQ developers.

    However in the end we still need to consider the way in which speed is measured - ISO vs Zone System vs etc.

    In fact, given Stephen's in depth knowledge of speed methods, it might be interesting to look at some of the curves we generated with my experimental high speed/low gamma developers. You may recall at the time I tried to make the point to Alan that all we could really do is compare toe shapes and fixed density points to some reference (XTOL normal CI in my case). ISO, fractional gradient, etc. would all seem to fail in extreme cases like that, and quantification becomes problematic.

  7. #37
    Rudeofus's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Crawley would tend to lean more in your direction, since he "felt" the true inherent speeds of films were higher than people were all used to at the time. This seems to be based mostly on the fact he was big into Phenidone, which tended to give small increases in properly balanced formulas, vs comparable MQ developers.
    Note that all/most developers released by Kodak/Ilford/Fuji in the last couple of decades are based on Phenidone/Dimezone-S, too. That was not some fad pursued by Crawley alone.
    Quote Originally Posted by Michael R 1974 View Post
    In fact, given Stephen's in depth knowledge of speed methods, it might be interesting to look at some of the curves we generated with my experimental high speed/low gamma developers. You may recall at the time I tried to make the point to Alan that all we could really do is compare toe shapes and fixed density points to some reference (XTOL normal CI in my case). ISO, fractional gradient, etc. would all seem to fail in extreme cases like that, and quantification becomes problematic.
    Normal developers are meant to be used more or less as the ISO speed definition requires, i.e. for normal contrast development. That's why this definition of film speed makes sense. You have seen yourself that if you force a film developer to lower contrast, you will sometimes shift the toe to the right (e.g. your Xtol N-x test), and sometimes not (e.g. your own LC devs). This means you'd have to use a modified version of ISO speed measurement for the contrast you are after, and possibly with a different number for how far the speed point lies above b+f.
    Trying to be the best of whatever I am, even if what I am is no good.

  8. #38

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    Yes, it does seem with reduced development sometimes the predominant effect is a lateral shift of the curve vs a decline in the gradient. Delta-X criterion (Stephen posted a good document) shows an important relationship between speed and contrast.

    Stephen, lucky you had access to someone like Dickerson. I've said before I wish I had at least occasional access to people like Dickerson, Zawadzki, Levy, etc. Too bad Bill Troop isn't on here anymore either. I sometimes wonder what it would be like, for example, Jones was still alive, what he might think of discussions like this. Or maybe he'd just laugh in our faces.

  9. #39
    Bill Burk's Avatar
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    My original reason for starting this thread was the relative speed difference between two different films TMY2 and Panatomic-X which didn't jibe with their difference in ISO.

    Now the surprise is that my 0.10 speed point shifted about 1/3 stop between two tests of the same batch of film 100 TMAX.

    Only difference in my process was how much time elapsed since the developer was mixed

    This is similar to Fred Aspen's case of a certain brand of distilled water killing his developer, except in my case this is not a dramatic drop in speed.

    Another surprise is the development time is the same and the gradient is the same, 0.62 CI, in both cases and both meet the ASA triangle.

    Yet the 0.10 speed point differs by 0.13 LogE units between the two. I have a tentative conclusion that the older developer did not attain as much speed as fresh developer.

    We've established why I trust the EG&G sensitometer, so I don't believe the shift is an exposure difference.

    If there isn't another explanation, I'll work under the assumption that the balance between the different developing agents and buffer changed over time. I guess it's time to start documenting my pH as I go.

  10. #40
    Bill Burk's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    I get an EI of 200-250 for Tmax 400 in D76 1+1 as well but why does that matter to you if you are satisfied with negs and results? if EI250 gives you all you need and has sufficient shadow detail, go for it.
    This thread documents how I calibrate my sensitometer, so it's important to know the film speed so I can work backwards to deduce the exposure. But that's theory. In practice you are right, it doesn't matter - because when I use EI 250 on my meter... my shadows have the detail I want.

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