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Thread: Calibrating 4x5; gray card Zones don't match still life Zones

  1. #41

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    Re: Calibrating 4x5; gray card Zones don't match still life Zones

    Quote Originally Posted by faberryman View Post
    How are you guys getting 1/3 and 2/3 stop exposure changes? On my Schneider lenses, the shutter speeds are at fixed 1 stop intervals, and while the apertures are continuously variable, only full stops are marked. If you get an exposure reading of 1/8 at f18, do you move the aperture lever as smidge past f16? How confident are you about the accuracy of your smidges? Are the shutters on all of you lenses calibrated so you know if they are a 1/3 step over or under (or worse)?
    Simple: If I need 2/3-stop more exposure, I'll set the shutter speed to the next lower setting (e.g., from 1/15 to 1/8 second) and then adjust the aperture smaller 1/3-stop from it's original position. Sure, there are no intermediate apertures marked on many shutters, but that's not an insurmountable problem; just eyeball the proper position. If you miss, it's likely to be only by a much smaller fraction of a stop, say 1/6 stop or less, which will have virtually no impact on a B&W negative.

    By the way, I use third-stops for all my testing, therefore the adjustments in the same increments. I test my shutters regularly and mark the actual speeds to the nearest third-stop. Estimating third-stop increments by eye with the aperture setting is fairly accurate too. That said, I'm well aware that the margin of error in exposure likely sometimes exceeds my attempts at third-stop accuracy. Nevertheless, trying to be as accurate as practical helps keep the margin of error as small as possible. I use third-stop increments because film speed and most curve charts, etc. use third-stop increments.

    If you don't want to go to the trouble of estimating between-stops, just use what's convenient for you. As long as you err on the side of overexposure, a third, half or even a full stop overexposure won't hurt anything. I wouldn't hesitate to use a full stop extra instead of 2/3-stop, since that's only 1/3-stop more, and will have no practical effect on the printability of the negative. However, I'm usually trying to squeeze out a bit more DoF and even a 1/3-stop smaller aperture makes me feel better.

    Best,

    Doremus

  2. #42

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    Re: Calibrating 4x5; gray card Zones don't match still life Zones

    Quote Originally Posted by neil poulsen View Post
    I appreciate the input on this, which I will bear in mind.

    As to my own practice, I rarely use N-2, mostly N-1, N, N+1, and once and a while greater expansions. For shadows, I may consider what I can expect for a Zone III area in a scene, but I like to expose for Zone II. Less change in speed that way. (Lower on the toe.) Not entirely sure about the wisdom of this; it's just what I do.

    As for testing B&W film speed using the 0.1 fb+f methodology, perhaps one can think of this analogously as lowering color film speed somewhat from that recommended by the manufacturer, so as to make sure that there's sufficient detail in the shadows. This is a common practice in color negative photography.

    I've always thought that "0.1" for B&W film was selected as the smallest value that minimizes the exposure needed to, none the less, provide sufficient detail in the shadows. In this regard, shooting B&W film at the mfg. recommended film speed just doesn't cut it. At least, not for me.
    Neil,

    The Zone System is primarily a system for visualizing tones in the final print and then making sure the negative contains the info one needs (exposure) and is developed so that it is the easiest possible to print (development). Placing a shadow on Zone III, or II or I, or even IV or V is an interpretive decision. I like shaded snow on Zone V a lot of times. Dark shaded doorways often get Zone II placement from me. If I need something really black, I'll place it in Zone I or even 0, depending on where everything else falls. The main thing is to know that whatever placement you use will get you the information in the negative in the right place in relation to the other luminances in the scene. Choosing development is similar; we want the easiest neg to print with the tonal separation on the neg that we desire, even if it requires significant printing manipulations (note, often this latter makes for what many ZS users would call overdevelopment).

    When I make exposure adjustments for expansions and contractions, they are based less on the ZS speed point and more on keeping shadow information and separation. Additionally, I often indicate N- developments in conjunction with an expected printing with a grade 3 or 4 contrast grade; this latter to maximize tonal separation in adjacent tones (micro-contrast if you will). These negs, then, are developed even less than a contraction neg designed for grade 2 or 2.5 and need more exposure support for the shadow separation.

    BTW, the 0.1 above fb-fog for B&W ZS use is the Zone I speed point, and should print close to max. black. Zone III density is quite a bit higher than this.

    Best,

    Doremus

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