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  1. #41

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    Quote Originally Posted by Michael R 1974 View Post
    I hate to be a stickler, but how do you know know D-76 does not produce "full rated speed"?
    The ASA standard developer was more active than D-76 using sodium carbonate as the alkali. High solvent metol based developers appear to produce slightly less film speed. Once diluted 1+1 the film speed improves. At least this was the conventional view when photo mags were popular. I remember Tri-X being rated at 320 with D-76.
    Last edited by Gerald C Koch; 04-30-2014 at 02:24 PM. Click to view previous post history.
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  2. #42
    Ian Grant's Avatar
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    Quote Originally Posted by Gerald C Koch View Post
    High solvent metol based developers appear to produce slightly less film speed. Once diluted 1+1 the film speed improves. At least this was the conventional view when photo mags were popular. I remember Tri-X being rated at 320 with D-76.
    I agree with you and Michae, back in the 70's when I used ID-11/D76 it was the norm with professionals to shoot FP4/HP5/Tri-X etc at a a third of a stop lower (sometimes a half) than the box speed because this gave better shadow details. Later I switched to Adox Borax MQ which is closely related to the ASA developer and that gave box speed as well as finer grain and better tonality (longer scale) because it was cleaner working (lower base fog).

    When I needed to push process HP5 (which I used for photographing rock concerts) I used ID-68 (Microphen) only stopping when Ilford released XP1 then later XP2 which I push processed in C41 chemistry.

    It's interesting that Kodak had the old ASA part of the ISO changed because Tmax films couldn't reach the claimed ISO using the previous testing standard. Ilford use a practical set of tests to determine ISO ad developing times.

    EFKE are now defunct but their ISO speeds were based on their films performance in Tungsten light and that goes back to the previous manufacturers if the films Dupont and prior to Dr C. Schleussner Fotowerke GmbH. So EFKE KB/R/PL 25 (new ASA name), 14 (old DIN name) is the Tungsten speed.



    The speeds went up slightly when the boxes & packaging were changed to reflect their speed in ID-11/DS76 rather than FR 5 which is similar to D23.

    It was once common for manufacturers to publish 2 ASA speeds, Daylight and Tungsten although the higher one was used on the box and cassette/backing paper. With slightly less Red sensitivity there's a bigger difference between the Tungsten speed & Daylight speeds with the old EFKE films.

    Ilford give 2 ISO speeds for Ortho Plus Daylight & Tungsten, they also state in their datasheets for other films that the ISO's are for Daylight, there won't be a full stop drop and there's so many variables you need to learn by experience or testing how much extra exposure is needed (if any).

    Ian

  3. #43
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    Well, there are 2 points here to address.

    I usually shoot all negative films about 1/3 stop slower than box speed so as to get better overall latitude. So, a 400 speed to me is a 320.

    And, when you push for speed, you are not reallly getting more speed, you are getting higher contrast and less latitude, but the mid scale and lower scale densities are higher thus giving a denser negative at higher speed setting. This is both good and bad. Good, in the sense that you can expose a 400 speed film at 800 or 1600 and get a good image, but bad in the sens that you lose latitude doing so.

    Now, thinking about it, I wonder of the release tests were done with D76 1:1. I never really thought about that one as most all workers used it straight.

    PE

  4. #44
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Interesting how almost "anti-box speed" people are. Even granting people are disinterested in the basis for ISO speeds (since it seems people tend to view it as some laboratory thing of little practical use in the making of real art, or as a marketing trick), I wonder how many of them are getting what they think they are getting when it comes to the various methods of establishing a personal EI.
    Michael, exactly my thinking. One of the problems with these types of threads is that there are at least 2 topics being discussed. One is about film speed (especially a speed standard) and the other is about a personal EI.

    The ISO film speed standard is a fixed density method that under specific contrast conditions will yield speeds based on the fractional gradient point. This methodology is called the Delta-X Criterion. The fractional gradient point is the minimal point of exposure where the film produces the minimum gradient sufficient for producing an excellent print (it's not 0.10 over Fb+f). It is the film gradient and not film density which is determinant of print quality. By knowing where the factional gradient point lies, exposure or a personal EI can be determined base on what's important to the individual.

    For those who point to the difference in the ISO gradient and the gradient for the statistically average normal, film speed changes little with developmental changes when it is based on gradient like with Delta-X and the fractional gradient method. In fact, according to C.N. Nelson in Safety Factors in Camera Exposure, in comparison to the Delta-X Criterion speeds "the fixed-density criterion tends to underrate films that are developed to a lower average gradient and to overrate films that are developed to a higher average gradient."

    So as Michael points out, not only are people not getting what they think they are getting, but for those who think the "box speeds" are wrong only think so because they are themselves using methods that are producing inaccurate results.

  5. #45
    Ian Grant's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    So as Michael points out, not only are people not getting what they think they are getting, but for those who think the "box speeds" are wrong only think so because they are themselves using methods that are producing inaccurate results.
    Box speeds are actually just a starting point, after all Kodak actually recommended using Tmax 100 at 50 EI for greater tonality. What's more important is what EI gives you the results you require and that may not be the box speed.

    Ian

  6. #46

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    Quote Originally Posted by Ian Grant View Post
    Other way round you mean increase the exposure by decreasing the Effective film speed (EI - exposure index) - to give better shadow detail.

    Ian
    Thanks for the correction Ian! I got stuck between "increasing exposure" and "decreasing EI" and just made matters more confusing! Hopefully the OP figures it out.

    FWIW, it seems pretty well-established that reducing developing times significantly from standard (whatever that is now, since every manufacturer can decide for itself), for whatever reason (contrast control, personal EI, etc.) will reduce effective film speed. With that in mind, it only makes sense, sensitometrically, that if one develops to a lower contrast index, one's personal E.I. will be lower than ISO speed. Mine are, but just a bit: I shoot 320 Tri-X and TMY at E.I. 250. I'm sure my metering techniques and light meter come into play here as well, but that's the point, isn't it? My personal E.I. should give me negatives that have the shadow detail I want and print like I want. I don't really think that I am using methods that produce inaccurate results by doing so.

    For color film, even with "standardized" development, there is still the question of metering and meters in general. Not only do individual metering practices vary, so do the light meters themselves, due to design or manufacturing tolerances. I know I have a hard time finding two meters that agree completely. That in itself should prompt everyone using a meter to find their own personal E.I. This is not denying ISO speed, simply compensating.

    If I am going to err when shooting black-and-white negatives, then it will be on the side of overexposure. I'm not really interested in "living on the edge" of not getting enough exposure. LF black-and-white film does fine with more than minimum exposure (sometimes better in the case of 320Tri-X).

    In any case, the negative is just an intermediate step to get a good print. I'm pretty sure the viewers of my work don't go around saying, "Oh my, he must have shot that at different than box speed!" If box speed is giving you the shadow detail you desire with the way you work, fine. If not, change your personal E.I. to compensate.

    Best,

    Doremus
    Last edited by Doremus Scudder; 05-01-2014 at 06:32 AM. Click to view previous post history.

  7. #47
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    Quote Originally Posted by Doremus Scudder View Post
    I'm sure my metering techniques and light meter come into play here as well, but that's the point, isn't it? My personal E.I. should give me negatives that have the shadow detail I want and print like I want. I don't really think that I am using methods that produce inaccurate results by doing so.
    Fully agree.

    The problem that pops up though here on the forums, and in real life ,is when "I" suggest my EI as a remedy to "my buddy's" problem, these suggestions become the root of myths and legends.

    The ISO standard gives us a way to "talk the same language". From there we can figure out how our processes differ.

    Quote Originally Posted by Doremus Scudder View Post
    For color film, even with "standardized" development, there is still the question of metering and meters in general. Not only do individual metering practices vary, so do the light meters themselves, due to design or manufacturing tolerances. I know I have a hard time finding two meters that agree completely. That in itself should prompt everyone using a meter to find their own personal E.I. This is not denying ISO speed, simply compensating.
    I do have two Sekonic L-358's that match.

    When I decided to use incident metering as my standard I interestingly found that my judgement about which tone went where when using reflective metering was more skewed than my reflective meters.

    Regardless of the meter in question though, testing is important. We need to know how our scene metering relates to the print.

    Quote Originally Posted by Doremus Scudder View Post
    If box speed is giving you the shadow detail you desire with the way you work, fine. If not, change your personal E.I. to compensate.
    Yep.
    Mark Barendt, Beaverton, OR

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

  8. #48
    markbarendt's Avatar
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    Quote Originally Posted by Ian Grant View Post
    Box speeds are actually just a starting point, after all Kodak actually recommended using Tmax 100 at 50 EI for greater tonality. What's more important is what EI gives you the results you require and that may not be the box speed.

    Ian
    Similarly Ilford suggests extra exposure for XP2 to reduce grain.
    Mark Barendt, Beaverton, OR

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

  9. #49
    Stephen Benskin's Avatar
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    Quote Originally Posted by Ian Grant View Post
    Box speeds are actually just a starting point, after all Kodak actually recommended using Tmax 100 at 50 EI for greater tonality. What's more important is what EI gives you the results you require and that may not be the box speed.
    Are a starting point for exposure not film speed. I believe I made this point in my post. The ISO speed gives you information from which to make a personal EI choice.

    Doremus Scudder
    FWIW, it seems pretty well-established that reducing developing times significantly from standard (whatever that is now, since every manufacturer can decide for itself), for whatever reason (contrast control, personal EI, etc.) will reduce effective film speed. With that in mind, it only makes sense, sensitometrically, that if one develops to a lower contrast index, one's personal E.I. will be lower than ISO speed.
    It's a very common misunderstanding. Film speed isn't determined by density because negative density by it self isn't relative to print quality. Film speed is determined by gradient. The fixed density of the ISO standard is a short cut to determining the fractional gradient point. As per Nelson, the fixed density method is only accurate when the contrast falls within the ISO contrast parameters. Otherwise you need to plug ΔD and Δlog-H into the Delta-X equation because with increased and decreased negative development, the fixed density method is less accurate. You're probably conflating it with how an increase in film density usually is accompanied by a higher gradient. This isn't always the case and definitely not to the same degree in different film types. This is all explained in Simple Methods of Determining the Fractional Gradient Speeds of Photographic Materials by C.N. Nelson and J.L. Simonds. If the OP really wants to understand what the REAL ISO is about, this is the paper.

    As for a personal EI, whatever makes you happy.

    The statement that very manufacturer deciding for themselves what the contrast for the standard should be is patiently wrong. The contrast parameters are clearly defined in the standard. Any variation and the ISO prefix cannot be used.

  10. #50

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    Quote Originally Posted by Photo Engineer View Post
    I usually shoot all negative films about 1/3 stop slower than box speed so as to get better overall latitude. So, a 400 speed to me is a 320.
    Latitude on the low end, to me suggests you are giving yourself an additional safety factor because of how many variables there are in metering etc.

    This is different than why most people down-rate their B&W negative films. The common argument is they get better shadow detail - implying better overall print quality. This is where I'd repeat people likely don't know what kind of negatives they are actually making vs what they think is happening. It's an issue with how people read/interpret/mis-interpret all the various methods out there in the Zone world etc. We tend to come away from those methodologies thinking we are "smarter" than we actually are. Like "aha, now I know how to find the real speed of my film, not the BS Kodak tells me, which must be why my prints always sucked".

    So this goes back to my earlier question - how do people know D-76 doesn't produce "full rated speed"? How are they even defining "full rated speed"? Is isn't just a density above B+F. There is a required gradient over an exposure range.

    I'm not saying it is wrong to shoot at half box speed. That's fine. I just think very few people really know why they are doing it. For a long time I certainly didn't.

    I'm not saying people need to learn about any of this to make good prints either. There is enough latitude and error throughout the end-to-end process for lots of approaches to lead to excellent results. The only reason I initially brought all this up is the title of the thread: "Box ISO rate and Real ISO". Barring extreme procedures, baloney developers and stuff, if you say the real speed of your ISO 400 film is 160, you should be able to back it up.

    PS: Glad to see Stephen post to the thread!

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