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Thread: exposure blues

  1. #11

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    Re: exposure blues

    There are too many variables for any of us to give you a viable answer. Can you post an image of the negative and resulting print? Below is a list (perhaps not complete) for the sake of understanding many of the variables and by no means is a suggestion that you are doing anything wrong. A combination of slight errors in several of these may culminating factors.

    1) Exposure issues
    A) Malfunctioning/un-calibrated shutter
    B) Wrong aperture
    C) Changing lighting conditions
    D) light meters are calibrated to expose for zone IV (not zone V like we all believed).
    E) lens flare

    2) Film issues
    A) fogged due to age or storage conditions
    B) chemical fog
    C) personal film speed needs adjustment

    3) Processing issues
    A) wrong temperature
    B) inadequate/too aggressive agitation
    C) contamination
    D) darkroom light leaks (see fogging)
    E) Fixer is too strong/too weak

    3) Enlargement issues
    A) paper may be fogged
    i) light leaks in darkroom causing fog
    ii) age
    iii) stored in too warm and or too humid an environment
    B) stray light from enlarger
    C) dirty lens
    D) wrong exposure
    E) wrong contrast

    4) improper print development
    i) wrong dilution
    ii) too cold


    I see nothing wrong with metering the skin and placing the value on a particular zone. The concept behind the zone system is to place values where we would like them to be and understand if the contrast scale will fit on the film and paper we choose. The zone system is a method for understanding and controlling contrast and value placement. If I'm shooting a high key portrait it is highly unlikely anything in the image will fall below a zone IV so I would not bother with placing shadows on zone II or III. I would suggest some testing on your part to determine a personal film speed and proper film development time. Even if something in the mix is off due to calibration you'll have a personal exposure system to get consistent results and a baseline. Right now there are just too many variables to consider.

  2. #12

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    Re: exposure blues

    Quote Originally Posted by Mrportr8 View Post
    D) light meters are calibrated to expose for zone IV (not zone V like we all believed).

    Hello,

    After reading that I got surprised and searched.

    here https://en.wikipedia.org/wiki/Zone_System

    it says:

    "note the meter’s recommended exposure (the meter gives a Zone V exposure)."

    Is there a debate about this?

    Regards

  3. #13

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    Re: exposure blues

    Quote Originally Posted by Pere Casals View Post
    Hello,

    After reading that I got surprised and searched.

    here https://en.wikipedia.org/wiki/Zone_System



    it says:

    "note the meter’s recommended exposure (the meter gives a Zone V exposure)."

    Is there a debate about this?

    Regards
    It will take me a day or two but I will find the source material for that statement and share it here.

  4. #14

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    Re: exposure blues

    Quote Originally Posted by Mrportr8 View Post
    It will take me a day or two but I will find the source material for that statement and share it here.

    "An early change in ASA (ISO) speed from 200 to 400, around 1960, was due to a change in the ASA standard rather than the film." (https://en.wikipedia.org/wiki/Kodak_Tri-X)


    What it is true is that current ASA/ISO standards underexpose an stop compared with 1955 norms to rate film speed: that change in standards happened in the 60s. So perhaps your statement comes from literature about ASA/ISO standard change...

    Until 60s photometers were way more uncommon than today, and film ASA/ISO speed rating had an additional stop of extra latitude for underexposure, as a "safety factor" for the uncertain Sunny 16 rule (I concluded, so IMHO). https://en.wikipedia.org/wiki/Sunny_16_rule

    Note that Sunny 16 works very well in a sunny day, because we have always near the same sunlight power of some 700W/m2 (UV-IR included, and a bit location dependant...), solving some metering problems as it is based on incident light...



    Thanks, this is interesting. At the end a lot of people use ISO 320 as 250 or ISO 100 as 80... Perhaps it is because there was that change in ASA rules...

    To me, I try to figure that density vs lux second curves combined with spot meter explains all, also ISO specs for film and photometers are there, and anyway practical recommendations are also there...


    Regards

  5. #15

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    Re: exposure blues

    Quote Originally Posted by fralexis View Post
    Doremus, thank for your answer. Makes sense. That is what I do with landscapes and I suppose portraits are no different. However, that brings up a question for me. Just how do most people determine exactly which shadows need zone III? Sometimes a particular shadow might be interesting, but exactly where to spot meter? I suppose that is a part of the learning curve. It doesn't seem to be intuitive. I am thinking of a low key protatit in particular.

    Alexis
    You may find the following procedure useful. I think most exposure/development failures happen because of 'mindlessness'. We reflexively think a 'subject' has a 'correct' exposure and development. It doesn't - there is only an exposure and development that makes it easy or difficult for you to make your final print.

    Keep in mind that photo paper can probably show about 7-8 stops equivalent worth of difference in density - a typical Dmax is around 2.0. Most of the real world can have quite a bit larger range. This means you really want to start by thinking about how you want your final print to look. In other words, think of your process as being a tonal window into a very wide tonal world. You are deciding which bit of the tonal range to pay attention to. You have some limited ability to contract and expand that window but not a whole lot. It is analogous to using your camera frame lines to determine which part of the physical world you want in, and out, of your final print.

    In other words, do not think of a 'correct' exposure for the subject. Rather a 'correct' exposure makes it easier to get the print you want. In a typical forest scene, you may have shafts of sunlight which are quite bright and shadows in the underbrush which are quite dark and you may be comfortable with letting those shadows in the underbrush go to black in the print. However, if you were doing a macro picture of the underbrush, you would not want those same areas to go to black. So, which is the 'correct' exposure for the underbrush? Hopefully the example illustrates that here is no 'correct' exposure - just one that makes it easy for you to express your print.

    I find it useful to make a quick pencil sketch of the subject - this is very, very rough and is really only meant to block in shapes. The reason I find this exercise useful is because it makes me very mindful of which are the big shapes in the composition and what level of density (darkness or lightness) each shape needs to be to make the print work. If you have difficulty focusing on the shapes because of the detail, try squinting your eyes to make them a little unfocused and suppress detail. Now you should be a in a good position to decide which of these shapes need detail - the darkest part that needs detail is usually placed around Zone 3. You can then measure the lightest part and see what Zone those would fall on if you gave an exposure determined by the shadow reading. If it is around Zone 7, most typical photo papers would comfortably produce that range. If not, you will try to develop to a slightly higher or lower contrast, so that the density of the negative matches what the paper would like to see. If higher, you can do an N-, if lower, you do an N+ development. Once this becomes second nature, you can fine tune further according to how you like your prints to look - some people like somewhat more 'contrasty' prints - they will use words like snap and clarity, others like a softer print - they will use words like subtlety and long scale.

    In the situation you describe, if you want the person whose portrait you are making to be printed with good contrast, much of the surrounding forest, which is presumably quite a bit darker will be very dark in the print and you may not care. Or you may want to show the person in relation to the forest, in which case, you would want all that detail in the forest but the person may become quite high key. You may have other controls (e.g., dodge/burn, making etc.) if you want to push and prod at the picture. But I think clarity at the time of making the negative is more helpful. Is the print about the person or about the person relative to the forest? They would dictate different kinds of exposures. A sketch can help to clarify those kinds of issues.

    Hope that helps, at least a bit. Cheers, DJ

  6. #16

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    Re: exposure blues

    "D) light meters are calibrated to expose for zone IV (not zone V like we all believed)"

    I could not find the original article where I first read this. It was most likely tossed out with some other old magazines. But here's what I recall. The author set out to discover why there was such disparity among light meters, even the same model/manufacturer when that part of photography is so critical. I was reading on Alan Ross' blog that he had three meters and had eventually sent them all out for calibration so they would agree. As it turns out (at the time of the article) there was no standard for meter calibration. The manufacturers more or less each determined how they thought their systems would best function and adopted their own standards. By and large, most of them settled on a reflectance value for middle grey in the 10% - 12% range rather than 18%. The reasoning was that most average scenes included foliage and sky in an almost even split. The sky would wash out when shooting transparency film (negative film can handle a higher contrast scene and it can be printed to an acceptable value more easily) so by lowering the target exposure a more pleasing image would result. Read almost any meter instructions and they tell you grass or foliage is 18% reflectance, middle grey. This makes sense with meters in-camera and spot meters where lens flare is a component, but only for those "average" situations.
    Now, if you do your own film tests with that meter and determine your personal film speed then this is irrelevant because the resultant film exposure index erases the error. In the end it does not matter if you rate Tri-X at 400, 320, 200 or 160 as long as you are getting good results and it is calibrated to your system (exposure, development, printing). If you skip film testing and calibrating YOUR SYSTEM then you are going to have a much harder time. I do not know if this carries over to incident meters as they are not affected by lens flare. Reflective meters without a lens system may also be different and were not covered by the article. I'll keep looking to find the original author but after a few days I doubt if my luck will improve.

  7. #17

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    Re: exposure blues

    Quote Originally Posted by Mrportr8 View Post
    "D) light meters are calibrated to expose for zone IV (not zone V like we all believed)"

    I could not find the original article where I first read this. It was most likely tossed out with some other old magazines. But here's what I recall. The author set out to discover why there was such disparity among light meters, even the same model/manufacturer when that part of photography is so critical. I was reading on Alan Ross' blog that he had three meters and had eventually sent them all out for calibration so they would agree. As it turns out (at the time of the article) there was no standard for meter calibration. The manufacturers more or less each determined how they thought their systems would best function and adopted their own standards. By and large, most of them settled on a reflectance value for middle grey in the 10% - 12% range rather than 18%. The reasoning was that most average scenes included foliage and sky in an almost even split. The sky would wash out when shooting transparency film (negative film can handle a higher contrast scene and it can be printed to an acceptable value more easily) so by lowering the target exposure a more pleasing image would result. Read almost any meter instructions and they tell you grass or foliage is 18% reflectance, middle grey. This makes sense with meters in-camera and spot meters where lens flare is a component, but only for those "average" situations.
    Now, if you do your own film tests with that meter and determine your personal film speed then this is irrelevant because the resultant film exposure index erases the error. In the end it does not matter if you rate Tri-X at 400, 320, 200 or 160 as long as you are getting good results and it is calibrated to your system (exposure, development, printing). If you skip film testing and calibrating YOUR SYSTEM then you are going to have a much harder time. I do not know if this carries over to incident meters as they are not affected by lens flare. Reflective meters without a lens system may also be different and were not covered by the article. I'll keep looking to find the original author but after a few days I doubt if my luck will improve.

    Phil Davis in Beyond the Zone System, Chapter 8, discuses that, talking if 18% or 12% because stray light it is the good photographic neutral grey...



    Norm ASA Z38.2.1-1943 details how film speed was calculated until 1960 and this contains how film is metered, since then ASA PH2.5-1960 was ruling and films then doubled displayed box speed without manufacturing changes. Wikipedia explains very well those norms https://en.wikipedia.org/wiki/Film_speed

    ...ANSI PH2.5-1979, without the logarithmic speeds, and later replaced by NAPM IT2.5-1986, the latest issue of ANSI/NAPM IT2.5 was published in 1993...


    And the end (if you have a not very contrasty scene) the film speed in combination with a calibrated photometer recommends an exposure that with "normal development" will deliver a negative that it is suitable to get a print with average 18% reflective density...


    For reversal film "ANSI PH2.21-1983, which was revised in 1989 before it became ANSI/NAPM IT2.21 in 1994, the US adoption of the ISO 2240 standard.


    I copy and paste all those standards to note that film exposure it is something very well regulated. I guess it was regulated like this for the sake of controlled results with highly automated 135 cameras.

    DX encoding not only was informing camera about film speed, also latitude was coded so the camera in matricial auto mode knew how to take advantage.


    A superb photometer it is the Nikon F5 one, Multi-CAM 1300, with a 1005 element RGB matrix, and a trained Neural Network intelligent system that never failed with Pro jobs. DX encoding and ISO standards provided an effective way to make all that work perfectly.


    Today what rules is ANSI/NAPM IT2.5 and this makes clear that if we expose like an standard photometer meters we'll get good prints. And also we know that a bit more exposure (negative film) it is always benefical if subject is static and we have a tripod, (also in abscence of strong highlights)


    And then there is what we can do beyond what the standard says

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