Grey card and Zone System

Discussion in 'Medium Format' started by steve_parrott, Dec 29, 2007.

  1. Sorry if I am posting this to the wrong forum, but I have not seen any that really pertain to this type of
    question, and I figure the MF film users here would be the best resource.

    I am gradually getting what I feel is a good understanding of the Zone System and how to use it. I use a
    Mamiya 645e with the center spot meter. Ok... I hope I can explain this so it makes sense.

    First I will get right to my question. Why does using a grey card to meter your subject give you a correct
    reading, when according to the Zone System, the objective is to CORRECT the meter reading which is
    setting the camera to acheive 18% grey?

    As an example: Say I want to expose correctly for some shadow areas in a landscape scene. I determine
    this area should be Zone 3. Ok... I take the meter reading, and according to the Zone System, I shoud
    set an exposure compensation value of -2 stops. That makes perfect sense to me, because the meter
    trys to place the shadow area up into the Zone 5 middle grey area, thus making it too light, ... so I use
    the negative exposure compensation to bring the exposure back down to where it really needs to be for
    correct exposure of the shadow area.

    So far so good. Now here is what I cannot get my head around. Perhaps I am wrong, but I am thinking
    that if you use a grey card, say on the same shadow area, and meter off that, then you do NOT have to
    make any exposure compensation. Is that correct?

    By using the grey card, are you still not placing the shadow area exposure up in Zone 5, where you DO
    NOT want it to be?

    I just cannot grasp how using a grey card can "override" using the Zone System for any selected
    metered
    area.

    I hope this made sense, and some kind folks here can "enlighten" me a little on this.

    Thanks so much.
     
  2. I suggest you read Ansel Adams book, "The Negative". After all, you can't better the explanation of the Zone system than that by the person who invented it.

    However, the Zone system was mainly invented to integrate the process of development with that of exposure, and you can't easily individually develop negatives taken with a rollfilm camera. So you can't implement the zone system fully while using your M645. It also doesn't tie in very well with the routine use of a grey card, since a grey card reading will simply give exactly the same exposure as an incident light reading, or a reflected reading from a mid-tone of the subject.

    To use the Zone system as Ansel Adams intended, and as you surmise, you really need to use a spot meter and take a reading from that part of the scene that you wish to print as "zone V", or middle-grey. Alternatively, you can meter another "key tone" in the scene and "place" that on a desired zone, remembering that the zones are approximately one stop apart.

    Another use for spot metering is to measure the highest important highlight and the lowest important shadow tone (those where you want some detail to appear). The number of stops (zones) between those two exposure readings can then be translated into a variation in development, in order to place the shadow and highlight tones at the extremes of the printable range of the paper.

    Anyway. All this is explained far more eloquently and in fuller detail in "The Negative". Any good public library or book shop should be able to point you in the direction of a copy.
     
  3. Use the card to help determine where zone 5 is in the scene. Then you can adjust. It is useful at the start to help,after a while you can determine without it.
     
  4. This is how I get my head around the grey card concept.

    If I meter off a grey card (assuming I have calibrated my film speed/film development protocols) and use the reading I get without modification then all mid-grey things come out mid-grey. This SAME exposure also means that all Zone 3 things come out two stops darker than mid-grey and, of course, all Zone 8 things come out 3 stops brighter than mid-grey.

    In short, if you PLACE mid-grey correctly then everything that isn't mid-grey will FALL in the correct place on the exposure scale.
     
  5. Steve asked, "Why does using a grey card to meter your subject give you a correct reading?"

    The gray card is Zone V (5), or "middle gray." All general photography light meters are designed to interpret whatever they "see" as that same middle gray. For example, if you have an average outdoor sun-lighted scene, and take a reflective light meter reading off of a gray card that's in the same sunlight, and set your exposure according to the meter, the resulting print will show the gray card and everything else in the scene pretty close to how it looked in "real life."

    If you want to get more details in the shadows, increase your exposure, but be aware that doing so will push ALL of the gray scale up. In other words, with a one-stop increase, dimly-visible details in the shadows of Zone II (2) will move up into more visible details in Zone III (3). Barely noticeable details in Zone I will move into slightly more visible Zone II. The problem is at the bright end of the scale, because it moves up also. One stop places the just-visible highlight detail of Zone VIII (8) into almost flat paper white Zone IX (9), and moves visible highlight detail of Zone VII (7) up into just-visible Zone VIII. That's often called "blocking-up" highlights, because the b&w negative's silver grains clump together and block the light from coming through to expose the paper, leaving it white in those areas.

    The common way around the blocked-up-highlights problem is to "expose for the shadows and develop for the highlights." That means, when you increase exposure to get more shadow detail, you give the film less development to reduce negative density in the highlights. That actually stretches the gray scale at both ends. Most pros just automatically "rate" their b&w film at a lower ISO, which effectively increases all of their exposures, and then they have their lab under develop the film. For example, Tri-X 400 "rated" at 200 (one stop over exposed) is very common (and gives beautiful results).

    Serious Zone System workers often throw in other variables such as the exposure/development response of different types of film ("characteristic curves"), and the activity of different developers, additives, temperature, agitation, as well as even more controls in the print room with split contrast printing.

    Steve stated, "...according to the Zone System, the objective is to CORRECT the meter reading which is setting the camera to acheive 18% grey..." I think what you mean by that is when you set your film exposure according to a reflected meter reading of a white piece of paper, that paper will be 18% gray in the print. If you want it to look white, you would have to increase your exposure by about three stops. I say "about" because the creative aspect of the Zone System is to put into your hands what color you want that paper (and everything else that's in the scene) to be. Or... you can just take a reading off of a gray card and everything will look "normal." However, as someone else mentioned, you don't really need a gray card. Once you can picture in your mind how different tones will reproduce in a print, you can point a spot meter at any reflectance value and keep it where it is, or move it up or down the scale. By the way... the gray card made by the Eastman Kodak Co. has two sides. Many people think the white side is just the "back," but in fact, it's made with the same careful controls as the gray side, and is used when the light is too dim for the gray card.
     
  6. Get "Zone VI Workshop" by Fred Pickard. It is the easiest read on the Zone System.

    With any light meter you have to know what it is calibrated to. Some are 18% (Zone V) and some are 36% (Zone VI). I'm not sure what the Mamiya meter is calibrated to.

    Most manufacturers would calibrate their meters to give a well exposed transparency as oposed to a B&W negative.

    Take a look at the "New Zone Manual". I use an incident hand held meter and avoid the problems with reading reflected light.

    You will have to run some tests of your own. Make sure you use fresh batteries when you do your tests.

    Good luck!
     
  7. "by Fred Pickard."

    Is that Jean Luc's brother?

    You are thinking of 'Fred Picker.'
     
  8. Thanks so much everyone for your help. That helps clear up things in my head. I really,
    really, appreciate it.
     
  9. .[. Z, Dec 30, 2007; 10:20 a.m.

    "by Fred Pickard."

    Is that Jean Luc's brother?

    You are thinking of 'Fred Picker.'



    Opps! Right you are! Can I claim a senior moment? :)
     

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