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  1. #21

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    Fair enough.

  2. #22
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    Quote Originally Posted by Stephen Benskin View Post
    Here's a funny thing about in camera testing and flare - there almost isn't any flare, and definitely not as much as in shooting conditions. I've attached a graph to illustrate this. There are two factors at work. First 80% of flare comes from the subject. Most in camera testing is done shooting a target with a single tone. Second, even considering average flare, the testing is done at the metered exposure point where flare has little influence on the exposure. The assumption that flare is incorporated into camera testing is almost universal. It sounds like it should be that way, but the use of a simple graph has proven it otherwise. Without such tools, the arguments can become an endless series of unsupported opinions.
    A question:
    The primer-----------In-camera testing these days, as we know, is the step wedge mounted on top of the film and the film exposed to a single tone target. I do mine outside on a sunny cloudless day in uniform shade so that the target luminance is steady when I make my exposures. But AA did not expose step wedges on film in the camera, he exposed only the negative(s) to a single tone in uniform shade to generate his speed tests and subsequent development times.

    The question-----------do you maintain that just as with a step wedge in the camera where you say flare is absent, or nearly so, that flare is also absent, or nearly so, from the negative without a wedge when AA did all his testing, or I should say, when Sexton did the testing under AAs guidance? Is there the same lack of flare condition at the film plane in both instances? Or, does the presence of the wedge itself inhibit some amount of flare from reaching the negative?

    Despite what you believe to be a pitfall in AAs ZS test procedure, you can't deny his results. He used lots of film and chemistry his way but speed determinations and curves were generated just the same---by reading the negatives with a densitometer and graphing the curves. The wedge, obviously, saves much film and chemistry in developing the same set of curves.

    Just curious.

  3. #23
    Bill Burk's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Fair enough.
    Spoken like a gentleman. Now are you going to give me a license for my pet fish?

  4. #24
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    Quote Originally Posted by Michael R 1974 View Post
    Fair enough.
    I am so sorry, I couldn't resist.

    Here's my real response...


    Doesn't mean you're wrong. Without opposing opinions this thread would not be much worth reading.

    A couple things you said struck me:

    You said it made things worse when you tried fitting negs to paper and I am curious to hear more about that. You've seen some of my thoughts on why that could be absolutely true.

    And you wondered about the value of two-place precision: My equipment gives two places. One place would be adequate. Since I have the two places, I find it easier to just write them as displayed. My aim point average is 1.02. Stephen's chart has LER 1.05 and 0.95. If I had rounded to 1.0 I might think my row was exactly in the middle. In fact "my" row is closer to 1.05.

    Sensitometry itself is part of my spirit - ingrained since the days of high school and Mr. Ford's print shop being called "pinhead" for not putting a Stouffer reflection scale on the copyboard. So it is part of the pleasure I get from my analog darkroom. It might not be fun for everybody - but it is second nature for me.

  5. #25
    Bill Burk's Avatar
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    Quote Originally Posted by CPorter View Post
    The question-----------do you maintain that just as with a step wedge in the camera where you say flare is absent, or nearly so, that flare is also absent, or nearly so, from the negative without a wedge when AA did all his testing, or I should say, when Sexton did the testing under AAs guidance? Is there the same lack of flare condition at the film plane in both instances?
    There is no flare in a sensitometer because it is contact.
    There is very little if any flare in a step wedge on film at the camera.
    There is some flare in a real traditional camera test - but not a lot because you are shooting a really, really flat subject.

    The criticism of camera testing is based on the fact that you are tossing otherwise separable variables into a mash.

    Shutter/lens/light source/flare/light meter - each can be measured with separate tests and added into the sensitometry results.

    I agree in principle with Stephen that variables are best excluded.

    But I also appreciate that camera tests (for example the Zone System as written in workshop manuals) teach the concepts in a practical way. So I withhold my criticism of the fundamental weakness of the approach for anyone who wants to explore this charted territory for themselves. I appreciate the journey and I respect anyone who wants to follow it for themselves. So if anyone wants to pretend it is 1884 again and I can offer assistance with the techniques of the time, I'd be thrilled to help.

  6. #26

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    Quote Originally Posted by Bill Burk View Post
    I am so sorry, I couldn't resist.

    Here's my real response...


    Doesn't mean you're wrong. Without opposing opinions this thread would not be much worth reading.

    A couple things you said struck me:

    You said it made things worse when you tried fitting negs to paper and I am curious to hear more about that. You've seen some of my thoughts on why that could be absolutely true.

    And you wondered about the value of two-place precision: My equipment gives two places. One place would be adequate. Since I have the two places, I find it easier to just write them as displayed. My aim point average is 1.02. Stephen's chart has LER 1.05 and 0.95. If I had rounded to 1.0 I might think my row was exactly in the middle. In fact "my" row is closer to 1.05.

    Sensitometry itself is part of my spirit - ingrained since the days of high school and Mr. Ford's print shop being called "pinhead" for not putting a Stouffer reflection scale on the copyboard. So it is part of the pleasure I get from my analog darkroom. It might not be fun for everybody - but it is second nature for me.
    Hi Bill, I wasn't trying to be sarcastic or anything with my answer. There just wasn't much to say because in the end I can't say anything Stephen writes on this subject is wrong. It is all sound and makes sense. It's also good information regarding the pitfalls of various testing methods and interpretations of results. I was just trying to question the utility of applying such precise sensitometry/densitometry to the end-to-end process of making a fine print.

    Regarding fitting negatives to the paper (actually there's a parallel discussion going on in the Barnbaum thread), what I mean is that people often come away from applied sensitometry (and/or zone system) methods with the idea that the total subject luminance range of the scene should be either expanded or contracted to "fit" within the scale of the paper. The print is viewed by reflection, and so the effective scale is shorter than the range which can be recorded on the negative. This is one of the first things we learn about the zone system. When the subject luminance range is long, we are taught to contract it to fit onto the paper. But this disregards the shape of the curve and the local contrast effects of modified development. Suppose important highlights fall on zone XI. The zone system says use N-3 to bring them down to zone VIII, which will print with detail. The problem is, when you contract a zone XI highlight (which must contain luminances above and below that for there to be visible detail) to zone VIII, you lose most of the local contrast in the negative. It might be easier to print the highlights, but they will show poor texture in the print, regardless of how dark you print them. At the same time, the midtones and lower values are reduced in contrast (even with increased exposure), making them harder to print, perhaps necessitating a higher paper grade. The bottom line is if we focus too much on the total density range without considering local contrast, we might come away with a negative that requires less burning/dodging to fit onto the paper grade, but doesn't contain sufficient information to make the print we envision. The more printing skill we have, the less we need to rely on matching the negative range to the paper range. It can therefore sometimes be better to let things fall where they may (perhaps using only N-1 in my example), and use printing controls to bring those high values down.

  7. #27
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    Quote Originally Posted by CPorter View Post
    A question:
    The primer-----------In-camera testing these days, as we know, is the step wedge mounted on top of the film and the film exposed to a single tone target. I do mine outside on a sunny cloudless day in uniform shade so that the target luminance is steady when I make my exposures. But AA did not expose step wedges on film in the camera, he exposed only the negative(s) to a single tone in uniform shade to generate his speed tests and subsequent development times.

    The question-----------do you maintain that just as with a step wedge in the camera where you say flare is absent, or nearly so, that flare is also absent, or nearly so, from the negative without a wedge when AA did all his testing, or I should say, when Sexton did the testing under AAs guidance? Is there the same lack of flare condition at the film plane in both instances? Or, does the presence of the wedge itself inhibit some amount of flare from reaching the negative?
    I assume the step tablet is in contact with the film. If so, then it is a non flare test.

    Generally speaking, average flare tends to increase or decrease 1/3 stop per stop luminance range. A one stop flare factor means that flare adds one stop of exposure to the lowest exposure. In the standard exposure model for 2.20 log subject luminance range ( 7 1/3 stops) using a 125 speed film, the shadow exposure will be 0.0034 mcs. One stop of flare will bring it up to 0.0068 mcs. The exposure at the metered exposure point will be 0.064 mcs. Add .0034 mcs of flare to 0.064 and you get 0.674 which isn't a big change.

    This is the condition in the camera image example I've included again. You can see there is very little flare at the metered camera point ( ~ 3% vs 100% in the shadow) and this is with a full 2.20 LSLR. When doing an in camera test of a single toned subject, the card is metered and stopped down. The flare at the metered exposure point doesn't change.

    I've also attached an example with a 4 stop subject luminance range. It's the shortest my program can do. You can see how flare is diminished as the luminance range is reduced. Now imagine flare from a single toned subject.

    Despite what you believe to be a pitfall in AAs ZS test procedure, you can't deny his results. He used lots of film and chemistry his way but speed determinations and curves were generated just the same---by reading the negatives with a densitometer and graphing the curves. The wedge, obviously, saves much film and chemistry in developing the same set of curves.
    You've always misunderstood my concern about this. It's not that you can't get good results. It's that you aren't getting what you think you are getting. It's good that the test is practically devoid of flare, but if you assume there's flare and there's not, it will skew the results. It comes down how to interpret the data. A film curve should represent the characteristics of the film and that means without the influence of flare. This means that you have to make adjustments for exposure conditions when extrapolating data from it - such as film speed and desired negative density range. (One advantage of using the multiple quadrant tone reproduction curve is the ability to separate the camera exposure from film curve.)

    With the ISO speed standard, that means placing the speed point 3 1/3 stops down from the metered exposure point instead of 4 1/3 stops which represents the actual shadow range. This difference in the point of measurement adjusts for one stop of flare with the camera exposure on a non-flare film characteristic curve. If you don't adjust for this and measure the film at the the 4 1/3 stop point, the resulting film speed will be one stop slower.

    So, as the in camera test is virtually flare free, and the Zone System says to stop down from the metered exposure point 4 stops, it suggests that you are interpreting a non flare testing condition without factoring in the adjustment. Since the Zone System only assumes 4 stops (vs the 4 1/3 stops for the ISO standard), the difference we would expect to see between the ISO film speeds and the film speeds from the Zone System tests would be around 2/3 of a stop. And this is exactly what we are seeing.

    As Seinfeld used to say, "not that there's anything wrong with that." This is were you tend to misunderstand my point. Doing this doesn't hurt image quality. You might recall how I tend to compare the Zone System testing results to the ASA speeds prior to 1960. Speeds were then a stop slower than they are today. Right there is the validation of quality from ZS testing. Speeds were a stop lower and quality was still good. You might also recall my point that while the ASA standard changed in 1960, Zone System testing didn't. This means that prior to 1960, film speeds from Zone System testing would have been generally equal with the ASA speeds. What we are basically discussing is that one of the testing methods changed and another didn't, which means they are no longer directly comparable. The reason for the change in the 1960 standard was to eliminate a chunk of a safety factor that they felt was no longer needed. A safety factor isn't a bad thing to have and there's nothing wrong with that.

    There are a number of additional factors that aren't addressed with Zone System testing, but flare has the greatest influence by far.

    My constant harping on the subject is to make people aware of how the system works. I think this is important to know. It's about how way we perceive things even though it might not have an affect on how anyone works. Understanding the Earth goes around the Sun and that the sunrise is just an illusion may not change the fact that I have to get up too early for work, but it does affect how I see the world. Think about how many theories have been created to explain why ISO speeds differ from the "true" film speeds obtained from personal testing. Now you know it's because the testing parameters are different - problem resolved, conspiracy theories vanquished. Yes, "film speeds" obtained by Zone System testing are technically wrong, but there is nothing wrong with them as EIs.

    The question of interpreting data for shooting conditions from data obtained from testing conditions also plays a part in the Zone System's approach in determining negative density range. In this case, there is an adjustment made, but it's never explained. So, while you get what you need, you aren't getting what you think.

    I hope this has clear a few things up.
    Attached Thumbnails Attached Thumbnails Zone System speed test.jpg   Four stop range - 2 Quad 1.jpg  
    Last edited by Stephen Benskin; 12-24-2011 at 02:00 AM. Click to view previous post history.

  8. #28
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    Quote Originally Posted by Michael R 1974 View Post
    Suppose important highlights fall on zone XI. The zone system says use N-3 to bring them down to zone VIII, which will print with detail. The problem is, when you contract a zone XI highlight (which must contain luminances above and below that for there to be visible detail) to zone VIII, you lose most of the local contrast in the negative.
    I appreciate your input and know you've been there and I want to hear more of your experiences.

    I am lucky some days (foggy Pacifica) to have 4 stops subject brightness. Just now I printed another flat neg. 0.53 is my negative density range. And I had to print it on Grade 3 because I used my last sheets of MG last night on a more precious print. I was lucky this neg exists too and you know, I have to have it framed tomorrow. So I printed this one high key and heavily burned the edges just to get something pleasing.

    It was roll film - and not developed long enough for the subject brightness range. I tend to develop roll film to CI 0.62 - have to check my notes to see what I did here. But I would have been better off tonight if I had developed this roll to fit my paper knowing it was a short-range day.

  9. #29
    Bill Burk's Avatar
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    Hey Stephen, Merry Christmas

    Quote Originally Posted by Stephen Benskin View Post
    the Earth goes around the Sun.
    The argument used to be.... If it did that, we'd be able to measure the parallax.

    Oh yeah, those stars are pretty far away.

    Bill

  10. #30

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    ...whatever works.

    I worked with a Print Master that knew so much science behind exposure, film developing and printing it was ridiculous. He even wrote a book on it and taught darkroom techniques for over a decade. He was even Annie Leibovitz's fulltime printer for a number of years. But when I'd hit the darkroom and ask for advice on certain negs, printing, shooting in various lighting conditions, his answers were very simple. I think the purpose of a theory like this is to dissect the science to such a degree that individuals can pick and chose what parts work for them and then develop their own formula for the prints they want to produce. This theory combined with experimenting can be a very valuable tool for photographers to understand all the variables and then choose what works for their own unique vision. If someone wants to strictly calculate everything or on the other side, strictly experiment with everything, great results can still be obtained. I personally have my own foundation of knowledge on the zone system calculated and I apply it to the field based on how I develop and print through experimenting and running various tests. Everyone will be different. Whatever works.

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