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  1. #51
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Perhaps I'm accidentally inventing the ISO standard for myself, or at least confirming it, albeit probably with the safety factor.

    Film speed as a target net density versus a reference point is an interesting issue when it comes to flare as well. I'm always told flare increases film speed. Well, in a way yes, but if the toe is flattened by flare, I haven't gained anything. In fact I've effectively lost "speed" because local contrast has been flattened in the shadows.
    Like with film speed calculation, what is considered the minimum useful gradient, while determined using a flare free test, has been adjusted to reflect the affects of flare.

    In my opinion most of the testing methods are more about producing a range of EIs that reflects the author's personal taste, whether it's about having enough of a safety factor, or producing enough shadow contrast, or producing a negative that works in conjunction of the just black printing test. For all but specialty developers, speed testing isn't really all that necessary and with specialty developers a simple comparison is between the two developers is all that is really required. It's more important to personalize the way the photographer likes to expose (personal EI) and that can be determined using the ISO speed as a foundation.

    I believe one of the reasons why there's such a fixation on speed determination is that with simplified Zone System method of sensitometric testing, you don't produce a curve, but only two points of density. In order to determine the contrast, you first need to find the base point. This is backwards from general sensitometric testing. There the film is exposed and developed to differing degrees. The contrast is then determined along with the effective film speed for that contrast. Has the simplification involved in such methods as the Zone System unintentionally overemphasized the importance of speed and a speed point and under emphasized of the importance of contrast determination? There seem to be far more discussions on speed and how to test for it then there are about contrast.

  2. #52
    markbarendt's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    There seem to be far more discussions on speed and how to test for it then there are about contrast.
    And when contrast is talked about it seems tied to speed point rather than SBR or preferred print contrast.
    Mark Barendt, Beaverton, OR

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

  3. #53
    Bill Burk's Avatar
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    From a recent family of tests I contact printed a negative image of a step wedge which fit the whole 21 steps on paper. (An original step wedge wouldn't do this - but a negative step wedge developed Normal would).

    I cut chips from the contact print to make a Zone System sticker for my Weston Master II meter last night.

    I wanted to include one stop of flare in my Zone System sticker, so I picked the next step above blackest black for my Zone 0 chip.

  4. #54

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    Quote Originally Posted by Stephen Benskin View Post
    Has the simplification involved in such methods as the Zone System unintentionally overemphasized the importance of speed and a speed point and under emphasized of the importance of contrast determination? There seem to be far more discussions on speed and how to test for it then there are about contrast.
    Well, the first thing I'd recommend to anybody using any kind of Zone System testing methodology is to produce a full curve, not just target a Zone I and Zone VIII density. To me, everything is about contrast - ie the shape of the entire curve since I am ultimately concerned with printing.

    As I've said, the speed point is a means to an end. I'm concerned with local contrast.

    But even when contrast is considered in Zone System testing, there should be a lot more discussion about local contrast (ie not just CI or Gamma) and the paper curve. After all, how many people come away from Zone System contraction methods (including extreme contractions) thinking N-4 necessarily means Zone XII will print with good detail because it has a Zone VIII density in the negative?

    But I'm getting ahead of the discussion there. We've sort of disagreed regarding the practical use of measures like CI in the past - mostly because I am typically dealing with significantly wider subject brightness ranges than average.

  5. #55
    Stephen Benskin's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    As I've said, the speed point is a means to an end. I'm concerned with local contrast.
    It is a means to an end, but that doesn't mean it's arbitrary. If done according to the ISO Standard, the speed point can yield useful information. It defines the relationship between the meter exposure and the shadow exposure, it defines the local contrast as well as determining the point of useful minimum exposure (0.29 log-H units to the left where the gradient is 0.3x the average gradient).

    This is what I mean about questioning the steps in any methodology. Most methods are just variations of the basic Zone System approach where the speed point is unconnected with the three elements list above. While the 0.10 density may have come from the ISO speed standard (the ZS use of 0.10 probably was derived from DIN or the early British standard), it has been misinterpreted or simply impoperly applied.

    Using the ISO speed standard we know the speed point is 1.0 log-H units to the left of the metered exposure point. According to many popular methods, the speed point is four stops down or 1.20 log-H units below the metered exposure point. Obviously the two methods will produce film speeds typically differing by two-thirds of a stop. This is why Zone System testing consistently produces EIs 1/2 to 1 stop slower than the ISO speed. While the 1.20 log-H method will produce quality negatives and will create perfectly acceptable EIs, it shouldn't be regarded as a reliable way to determine film speed. Of course, if the additional exposure from the lower EI matches your style, why not save the time and just use the ISO speed and make the 2/3 stop adjustment. Afterall, what's the point of doing the test if it's not going to produce a reliable number.

    Most of the authors won't explain this difference (mostly because they aren't aware of it), so when shopping around for a non-ISO testing method, understanding the theory is important. Just because someone wrote it down doesn't mean it's true. This doesn't mean you shouldn't use a non-ISO method. I'm just suggesting to use it knowingly.

  6. #56
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    To tell the truth I am bit lost here.
    Reading all this.
    All I can say is that I use the 0.1 speed point as my first reference. I plot my curves to see how the shape is. This is important for me. When I use my adopted method (a bit of this a bit of that) I can usually make my print at about Grade 2 (to simplify this using Grades), I increase the development times slightly because I like to use unsharp masks and the funny thing is I land at a contrast of about 0.62 which is what most published time use as a standard. However my actuall development times are always less than published and I always have to overexpose.
    I am always amazed and wondering when people say they use box speed. It doesn't make sense to me.

  7. #57
    Stephen Benskin's Avatar
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    Quote Originally Posted by AndreasT View Post
    To tell the truth I am bit lost here.
    Reading all this.
    All I can say is that I use the 0.1 speed point as my first reference. I plot my curves to see how the shape is. This is important for me. When I use my adopted method (a bit of this a bit of that) I can usually make my print at about Grade 2 (to simplify this using Grades), I increase the development times slightly because I like to use unsharp masks and the funny thing is I land at a contrast of about 0.62 which is what most published time use as a standard. However my actuall development times are always less than published and I always have to overexpose.
    I am always amazed and wondering when people say they use box speed. It doesn't make sense to me.
    My point is that it is good practice to critically question the details / theory of testing method they use or are considering using. I believe the testing results most people produce create a false sense of accuracy. They basically aren't getting what they think they are getting.

    Would you mind breaking down your testing process? You say you use 0.10 speed point. How do you test for this? Do you have a reference for the CI 0.62 that you say most published sources use this standard? Are you determining it yourself or have you chosen it based on a source?

    Why are you amazed people use box speed?

  8. #58
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    I have enlarged hundreds of photo for people. Artists and Photographer. Most od them use box speed. The results are aweful. So much trying to get a decent print. I lot of people do not change their exposure or development with thought according to the lighting situations.
    Basically I use a similar method used by Phil Davis in exposing film under an enlarger. Develop five or more testa at differnt times and plot them. I use a more contrasty "standard" to Phil Davis since I find his reults to soft to be practical.
    My aim is to fit my negatives to a Paper contrast of 1.05. As mentioned I usually increase my devolpment because of the use of unsharp masks. If I desire I do change my exposure according to what I want or need.
    Have to go dinner is being served. I will get back to this later.

  9. #59

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    Quote Originally Posted by AndreasT View Post
    I have enlarged hundreds of photo for people. Artists and Photographer. Most od them use box speed. The results are aweful. So much trying to get a decent print. I lot of people do not change their exposure or development with thought according to the lighting situations.
    Basically I use a similar method used by Phil Davis in exposing film under an enlarger. Develop five or more testa at differnt times and plot them. I use a more contrasty "standard" to Phil Davis since I find his reults to soft to be practical.
    My aim is to fit my negatives to a Paper contrast of 1.05. As mentioned I usually increase my devolpment because of the use of unsharp masks. If I desire I do change my exposure according to what I want or need.
    Have to go dinner is being served. I will get back to this later.
    Andreas - how can you be sure the awful negatives (and I must assume for now you mean underexposed when you say awful) are the direct consequence of these people having rated their film at box speed? What about how they metered their scenes, exposed the film, developed the film? There are many variables to consider.

  10. #60
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    Quote Originally Posted by Michael R 1974 View Post
    Well, the first thing I'd recommend to anybody using any kind of Zone System testing methodology is to produce a full curve, not just target a Zone I and Zone VIII density. To me, everything is about contrast - ie the shape of the entire curve since I am ultimately concerned with printing.

    As I've said, the speed point is a means to an end. I'm concerned with local contrast.

    But even when contrast is considered in Zone System testing, there should be a lot more discussion about local contrast (ie not just CI or Gamma) and the paper curve. After all, how many people come away from Zone System contraction methods (including extreme contractions) thinking N-4 necessarily means Zone XII will print with good detail because it has a Zone VIII density in the negative?

    But I'm getting ahead of the discussion there. We've sort of disagreed regarding the practical use of measures like CI in the past - mostly because I am typically dealing with significantly wider subject brightness ranges than average.
    I agree that producing a full curve is essential, especially since in the ZS, knowing the CI is not a relevant consideration for anything ......the films response to development is relevant along the entirety of the curve, not just by points on the curve connected by a straight line. Not to diminish CI, only that the specific value of CI has no inherent significance in the primary function of the ZS, which, as stated in The Negative, is to support visualization.

    I disagree on the extreme contractions statement, shadows can be given added exposure with the "placement", and compensation development used to support that added density in the low values while keeping good separation at the important higher values. I have only accomplished an N-3 contraction, but I have indeed accomplished it through highly dilute developer with hc-110 and reduced agitation, with TMX, albeit at a loss of film speed at EI 50. The preferred neg density range was effectively maintained. But perhaps I'm just misreading your intent on it.
    Last edited by CPorter; 01-16-2013 at 08:02 PM. Click to view previous post history.



 

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