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Thread: Determing correct exposure

  1. #51

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    Re: Determing correct exposure

    I've divided my system into three parts. Exposure, Development and Printing.

    My Print quality goal is to make a negative that falls between Grade 2 and Grade 3 paper (so that a "perfect" negative might work on either paper, but if too contrasty it would fit Grade 2 and if too flat it would be OK for Grade 3).

    My Development quality goal is to make clean, scratch-free negatives that are developed sensitometrically to the Contrast Index I call for. The CI is the easiest thing for me to hit. The clean, scratch-free quality remains what I can best term "expressive." I'm working on that.

    My Exposure quality goal is to place sufficient shadow exposure to get good detail in places that might normally be solid featureless black. I also try to keep highlights from blowing out. So I take my sensitometry results and "shift" my EI by 2/3 stop towards overexposure (I shoot T-Max 400 at EI 250). For nature photography I will use Zone System and place shadows on Zone II, I'll rate the film for N, N+1, N-1 etc. For special purposes I will use Zone System and make extreme placements for graphic effect. For newspaper reporting I will use incident readings and shoot as-recommended by the meter. Sometimes I will just set my camera as needed to catch the shot and deal with it by developing by inspection and printing on Grade 4.

  2. #52

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    Re: Determing correct exposure

    In my youth... 30+ years ago, this is basically what I did. I overexposed Agfapan to keep details above the toe (25 ASA was my favorite but often had to settle for 100), I decreased development in dilute Rodinal (1:100) for flat/dull negatives... to avoid pushing the highlights over the shoulder. But... I extended the film tonal range with selenium toner. Generally speaking I halved the rated ASA but there was some tweaking depending on total development time. I printed on Ilford Gallery #3 and selenium toned the prints too. This effectively placed most important detail on a fairly straight and extended H&D curve with very open but deep shadows and bright but detailed highlights. The results were fabulous, IMHO. But... I've been posting about this method for years and no one seems to believe it. <shrug>

    ETA: The above hoop-jumping is completely unnecessary with today's extended latitude emulsions and hybrid workflow. The old days are long gone... and good riddance. This is coming from a once died-in-the-wool analog wet-process old-school type. Please don't tell my APUG friends what a turn-coat I am.

    Quote Originally Posted by Ed Richards View Post
    > Ansel and John rate(d) their films at 1/2 the Kodak speed - in spite of Kodak, not in accord with them. They want(ed) fuller shadows, not a bold "commercial" look.

    Or perhaps, as Bruce Barbaum maintains, Ansel really put his important shadows on Zone 4 rather than Zone 3 - which is exactly what rating your film a half speed does. For reversal film, I use incident. For black and white, I use Xtol which gives rated film speed and I use the zone system. I was putting the shadows on zone 3 and not worrying about the highlights unless it is an extreme scene. If it was, then I would shorten the development. After reading Bruce's book, The Art of Photography, I started putting my shadows on Zone 4. The negatives are more dense, and I need to shorten development more often, but it really does work better.

    For black and white film, the key is enough exposure, and to always err towards over exposure. Incident meters are fine as long as you do not have important detail in shadows. If you do, I find my zone exposures to be 2 or more stops more light than the incident reading.

  3. #53

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    Jerry,

    You're getting lots of opinions here (as well as a little levity), some more considered than others and some more slapdash than others. Maybe some of my opinions and observations can help you better find the way you need for determining best exposure.

    I also think a good method for finding correct exposure is "hugely important"; not because you need to be extremely accurate with your exposure; negative film has lots of latitude, rather because "correct" exposure relates directly to your vision of what you want in the final print. I use my own version of the Zone System, but before I elaborate on that, I'd like to summarize and comment on the methods presented so far.

    At one end of the spectrum is the "make sure I have enough exposure" school. These photographers almost always use negative film, often roll film in quickly changing conditions. Their approach is to give full, even over-, exposure in order to ensure adequate shadow detail and then rely on variable contrast paper or Photoshop to deal with contrast. This approach works well for many, especially if the lighting is not extreme. Metering here is done by many methods: in-camera averaging meters, incident meters or using a reflective meter to read a shadow value or a mid-tone. Most often, their personal EI is somewhere around half of the manufacturers' ISO rating. Many who started with the Zone System but now print largely on VC paper or scan their negatives have switched to this method just because it suits their needs really well and eliminates some of the fiddleyness of the Zone System. It might suit yours as well.

    There is a school of careful incident metering that relies not on placing reflectance values like the Zone System, but deals with light intensity and the ratio between lit and shaded areas of the scene, e.g., "duplex incident metering." Incident meters are used to take readings in the main light and in the shade and then some calculations are done to come up with an exposure that retains shadow values. In the most complex of these systems, provision is made for development to the correct contrast. Phil Davis' incident metering scheme in his BTZS is the most precise of these. Again, many just make sure that they have enough shadow detail and rely on contrast controls in the post-processing/printing stage.

    Transparency film needs to more precise metering than negative film, since transparency materials have little latitude. Really, transparency film requires a basically different metering approach from negative films. With transparency film, the highlights that need to be considered when metering. Many meter the highest value they want detail in and then open up two stops to place that value in the "detailed highlight" part of the film. Shadows then just go black if the contrast range is too large for the film. Careful workers often measure the contrast range and then may pre-expose the film a bit to bolster shadow detail. For roll film users, bracketing is de rigueur when using transparency materials.

    Skipping the Zone System for present, the most precise and comprehensive exposure and development system is Phil Davis' Beyond the Zone System, (BTZS). With it, one tests film for a personal EI, plots curves for different film developments and paper grades to determine how the entire system functions with regard to subject contrast range, from film to paper. Knowing how the whole system works allows one to tailor each negative for the desired result. Metering is done using a sophisticated incident metering technique or a spot-metering technique to determine the contrast range, which is then entered into a hand-held computer to determine exposure and development time for the chosen paper. This system requires that you do the testing and carry around a computing device in the field. It seems to be used mostly by large-format, one-sheet-at-a-time photographers. Once mastered, the chances of exposure errors are very low.

    On to the Zone System: In the responses so far, the Zone System seems not to have fared too well. I think there is a fundamental misunderstanding of the Zone System by many, which leads them to reject it as either too complicated or too mechanical. Unlike other exposure systems, the purpose of the Zone System is not just to get all the information on the film; it is a visualization tool. Yes, you measure reflectances with a spot meter, but these you "place" or manipulate to get them where you want. This, I believe, makes it unique among exposure-determining methods. I find it surprising that so many read Ansel Adams photography series and come away without the word "Visualization" writ large in their minds, for it is precisely this aspect of the Zone System that makes it a different tool than other exposure systems.

    The Zone System is for careful workers who want more control of their final print values. I don't think it works well for many types of photography; I wouldn't use it for street photography, sports, weddings, etc. But, for a more contemplative type of photography with subjects that are not so mobile, and when the photographer feels that the relationships of tonal values is an important element in the final product, I find it invaluable. Like all of the more sophisticated exposure-determining systems, one needs to know the characteristics of one's materials and processes. In the Zone System, though, one uses this knowledge to evaluate a scene, visualize a final product, and then tailor the entire process, first exposure and development and later printing and finishing, in order to achieve this visualization.

    Learning the feel and the look and the expressive qualities inherent in the interplay of tonalities in a final print, and how to translate a scene into a personal expression consisting of shades of gray is the heart of the Zone System. It is therefore, not for those who do not need or wish to do this.
    For me, however, it is exactly what I want. The technical aspects of the system are really simple in concept. One needs to know just a few things: How fast is my film really, so I know, when I place a value in Zone II or III, that there will be the detail I expect there? How much development do I need in order to get the mid-tones and highlight values where I want them to be? And finally, what is possible to achieve with the tonal relationships (and impossible)?

    Unlike even the BTZS, the Zone System allows me to depart radically from normal tonal renderings. If I want that bright shadow to be jet-black in the print, I know how to do that, and keep the highlights high enough so they don't print gray. If I want a feeling of luminance in the shadows, even though they are really dark and the rest of the scene is lit with harsh sunlight, I can do that too. Important here, again, is that one "wants" to do something with the scene other than just record it.

    Keep in mind that the Zone System was developed years ago when graded papers were the norm and digital was not even a dream. Tolerances then were necessarily a bit tighter than they need to be today. That said, it really isn't much harder to be precise and, if one prints analog still, making the best negative possible is still a worthwhile goal. With modern materials and methods, however, one can salvage negatives that may have been difficult or impossible to print 50 years ago.

    When I learned the Zone System (I taught myself from Adams, White, et al.), I made Zone Rulers: little squares of photo paper from my own test negatives on the papers I used in each Zone and for each development scheme. I had a Zone Ruler for N, one for N-1, one for N+1 etc. I mounted them on mat board and carried them with me in the field. I used them as visualization aids so I could get a better idea of what the Zones looked like and their relationships. After a while, I could carry the Zone Rulers in my head.

    Now, I look at a scene and, instead of trying to figure out what exposure I need to hold shadow detail, or keep highlights from blowing out, I ask myself, how does it feel? How do I want to distribute my melody of gray tones so that I can make a print that communicates what I feel and what I want to say? (It does help to have some feelings and something to say...) If I feel I can make an expressive statement with a photograph, I have already decided to a large extent where I want the Zone placements to be. Then it is just meter-place-decide on development; easy. And, for a "classic" landscape with "normal" lighting, it takes about two seconds to do that. My meter is more a tool for me to determine the difference between "reality" and my visualization than an exposure-determining instrument. Sure, I use it to set the exposure, but that is simply mechanical. I don't carry gray cards or hand-held computers. I do have a spot meter and a notebook... and my brain.

    On different, but related subject, I advocate reading subject values through a spotmeter for the same reason as I use the Zone System: only that way can I get real information about what the tonalities are/will be for a given area (the sky, for example). And only with that information can I make the manipulations I need to get the tonal relationships I want.

    To conclude, I think that the metering technique one uses should fit the type of photography they do. For me, it's the Zone System. You have to decide for yourself what you need. Your technique only has to be good enough for your vision.

    Best,

    Doremus

  4. #54

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    Re: Determing correct exposure

    There's something we're not addressing here. Jerry says he's photographing a "dappled" scene consisting of very dark and very bright spots (caves in snow) I guess this is a very high contrast scene
    While film has wide latitude, paper doesn't. So the best exposure may still just not do it. And reducing contrast may result in grey snow.

  5. #55

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    Re: Determing correct exposure

    Awesome post Doremus. Really informative and thought provoking. Thanks for taking the time...

  6. #56

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    Re: Determing correct exposure


    Fallen Birch, 2012
    Tachihara Field Camera, 200mm Nikkor M
    4x5 HP5+, Pyrocat HDC

    Having used the Zone System for a long while, I recently switched over to a simplified form of BTZS, suitable for scanned negatives.

    In retrospect, with non-trivial subjects, I often had a hard time mapping parts of the scene to specific Zones. Duplex incident metering allows you to take that out of the equation, and frees you in a way, to concentrate more on tonality and the quality of the light itself.

    I made this photo yesterday - not the greatest, but I didn't have to give Zones a moment's consideration, but instead was able to let the subject "speak for itself". You might way it was able to "pre-visualize" itself better than I could have ever done.

  7. #57
    Chuck P.'s Avatar
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    Re: Determing correct exposure

    Ken-----

    First of all, stepping back several feet from this perspective and a forest floor scene like this (I assume that's what it is) would seem very chaotic and murderous to isolate-----I think you have done it very well here, I love this.

    Regarding exposure----I personally use the ZS and the decision, for me, is not deciding where a luminance "belongs", but where I wish it to be. The best example I have of this is here : http://www.flickr.com/photos/silverg...7623596782735/ . This represents a huge departure from reality. In your example, I'm quite content with the (as I view it) very literal rendering it has.

  8. #58

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    Re: Determing correct exposure

    Thank you - that's an excellent insight, and explains a lot.

    I'm sure this applies to many of us: our photos are basically "realistic" with regard to tonality, composition, etc. We find a subject that is already beautiful, and trust in the power of Large Format to do the rest. Every photograph is contrived, but these convey the impression of a literal rendering.

  9. #59

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    Re: Determing correct exposure

    Quote Originally Posted by Chuck P. View Post
    Ken-----

    First of all, stepping back several feet from this perspective and a forest floor scene like this (I assume that's what it is) would seem very chaotic and murderous to isolate-----I think you have done it very well here, I love this.

    Regarding exposure----I personally use the ZS and the decision, for me, is not deciding where a luminance "belongs", but where I wish it to be. The best example I have of this is here : http://www.flickr.com/photos/silverg...7623596782735/ . This represents a huge departure from reality. In your example, I'm quite content with the (as I view it) very literal rendering it has.
    Incident metering can be used very directly to determine the exposure settings but it does not preclude "artistic" placement of an exposure.

    All any metering method does is provide a reference point.

    How we relate any metered reference point to a camera setting, is simply a technical expression of an artistic choice.
    You can't depend on your eyes when your imagination is out of focus. ~ Mark Twain

  10. #60

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    Re: Determing correct exposure

    I want to thank everyone on their responses. Methods of exposure is at the base of knowledgeable photography. The willingness of the LF forum to share their experience is greatly appreciated. Again thanks.
    Jerry Cunningham

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