Help with the Zone System

Discussion in 'Large Format' started by jason l., Feb 4, 2002.

  1. Hello,

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    I am trying to evaluate Aristo ISO 125 8x10 film using the test procedures outlined by Ansel Adams in _The Negative_.

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    I am measuring densities with a Highland transmission densitometer.

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    My developer is Ilford ID-11 stock diluted 1:3 with distilled water.

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    I am getting a reading of 0.03 for film base + fog

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    Based on what I understand from Adams' book, Zone 1 should be at a density reading of 0.13. I can get about this density with the film rated at ISO 100.

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    It is also my understanding that an increase in density reading of .3 corresponds to a doubling of the density and thus to a 1 zone increase in density.

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    If this were correct, then I would expect that Zone 8 should correspond to a density reading of 2.23. (7 * .3) + .13 = 2.23.

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    However, on page 242 of _The Negative_ Adams stated that he found a density of 1.25 to 1.35 ideal for diffusion enlargers. By my reckoning, this density range is at bout Zone 5.

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    I am very obviously missing something critical here but I cannot figure out what it is. My step tablet that I bought from Phil Davis at Darkroom Innovations has 21 steps of .15 density increase each. The second step reads about .16. Going through the tablet you get .3 increase in density every second step. This means that on this step tablet Zone 8 would be at step 16; taking the second step to be zone 1. And step 16 on the tablet reads 2.26, very near to what I think Zone 8 ought to be but very different from what Adams states in the testing procedures.

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    The matter is further complicated by the fact that I cannot seem to get the density of Aristo 125 (rated at 100 and exposed for Zone 8) up beyond 1.95 regardless of development time.

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    I thought someone out there might have some insight into what I am doing wrong here.

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    Thanks for any information you can provide.

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    Jason Kefover
     
  2. Adams is referring to the density in the developed negative (not to
    the densities on the step tablet). The step tablet you are using is
    just a convenient way to approximate scene luminances (and you are
    correct - a 0.3 increase in density would correspond to 1 stop). In
    that sense, a density of about 2.26 would be about Zone VIII. The
    point is that these densities just approximate scene luminances
    (i.e., provide convenient 1 stop changes in scene luminance). The
    idea is to expose your negative material to these luminances and
    develop the negative. Your negative should have a density range of
    around what Adams suggests. So, one way to think of it is that you
    are going to compress the 2.26 range of density in the step wedge to
    a density of approximately 1.3 or so in your negative. Why the
    compression? Because enlarging papers have a density range they can
    accomodate i.e., exposure to a certain range of densities will
    produce a range of tone from white to black. Any density outside this
    range cannot be printed (well, without resorting to dodging and
    burning etc).

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    In fact, I would suggest you first print the step wedge onto the
    paper of your choice (use the process you will eventually use -
    contact or enlarging) and count the number of steps between white and
    black. That gives you the density range that can fit on the paper
    (let's say this is going to be approximately 1.2). Then you want to
    tweak your developing time till the 8 zone range (the 2.26 on the
    step wedge) provides that density range.

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    Hope this helps. Cheers, DJ.
     
  3. I assume you are referring to Arista film sold by Freestyle (and
    supposedly manufactured by other well known companies). Aristo (Grid
    Lamp Products - www.aristogrid.com) is a company that manufactures
    cold light heads for enlargers (and other medical, scientific, and
    industrial products that use fluorescent, neon, cold & hot cathode
    lamp technology). There is no relation between the two companies.
     
  4. You raise a very important issue, the only place I've seen this
    addressed is in a book from Kodak.

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    Our negatives, and prints, are compressed (that is, the overall
    contrast is reduced) when compared to real scenes. While a density
    difference of 0.3 represents a 1-stop difference, or a
    doubling/halving of the light level for any real scene, we purposely
    develop negatives so that this light difference is represented by a
    smaller density difference. This keeps a scene with a big range in
    light within the more limited density range that film and paper are
    capable of producing.

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    Your own measurement of this film shows that it cannot produce a
    density range of 2.4--it maxes out at nearly 2.

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    If you consider each step on your tablet as a zone, then the step
    tablet represents 50% compression--and 8 zones on this tablet gives a
    density range of 1.2, 9 zones gives a denstiy range of 1.35. Right in
    the neighborhood of AA's recommendation.

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    Try this: take your reflectance meter, and measure the black and
    white parts of your printing paper. (If you don't have a spot meter,
    print a fully black sheet of paper, and just fix a sheet of paper for
    full size sheets to meter). Take the log of the difference in stops
    of these two readings, and you've got the density difference your
    paper can hold. Now you know why this compression is needed.
     
  5. The Zone VIII that you are attempting to print refers to the amount of
    light striking the negative at the time of exposure, versus the amount
    of light passing through the negative during enlargement. (i.e. the
    density of the negative.)

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    The density needed to achieve a Zone VIII reflectance off the paper
    depends on the contrast of the paper. Adams is saying that he can
    achieve that for the "normal" paper that he uses at about a
    negative density of 1.25 to 1.35.

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    So, you would adjust the aperture/shutter to achieve a Zone VIII level
    of light, then you would expose the negative at this level of light.
    If you are obtaining the same results as Adams describes for an "N"
    (normal) development, then the density of your negative for this level
    of light would be between 1.25 and 1.35. If you were to print this
    negative on his paper, exposing it for just the time that it takes to
    achieve a maximum black, then it should print at about a Zone VIII on
    the paper.
     
  6. I think you're confusing absolute density steps with the gamma
    corrected density 'zones' that you get on a negative.<br>A one stop
    increase in exposure will only cause a 0.3D change in density if the
    film is developed to a 'gamma' of one, but this gives unprintably
    contrasty negatives. A more normal contrast or gamma value would be
    0.6 (ish), and this means that you get an increase of (0.6 x 0.3D) =
    ~0.2D for each stop or 'zone'. At least over the straight line portion
    of the film's characteristic curve.<br>Your mistake has been to
    assume that the film should give you a 0.3D change in density for each
    zone change.<p>In practise; it's rare to get a Dmax of greater than
    2.4 on fully fogged B&W film with normal development, and the highest
    printable density from a pure white region of a real subject usually
    comes in at around 1.8.<br>If your negatives are in this region then
    they'll print OK, and that's what it's all about, isn't it?<br>You've
    said "I can get about this density with the film rated at ISO 100." -
    So what more do you need to know? The zone system should NOT be about
    pointless and endless measurement of step tablets; it should be about
    previsualisation of the finished picture.<p>Two questions:<br>1) Why
    are you diluting ID-11 to 1+3?<br>2) To what purpose are you doing all
    this sentometric measurement?
     
  7. Jason,
    I struggled with the Zone system and found there are some inherent
    problems understanding the concepts, especially when you read a
    variety of authors. There are exposure zones, print zones, density
    zones, etc. Sometimes the concept is well defined; sometimes it is
    implied; and sometimes the definitions are missing. To keep my
    sanity, I devised a system called VIDEC that overcomes these
    shortcomings. The system is described in capsule form in a series of
    three articles I wrote for PhotoTechniques Magazine. I deliberately
    avoid the use of the word "zone". Instead, I lay out a logical path
    that accounts for the exposure delivered to the film, the degree of
    development and the resulting density. By use of a graph, you can
    work the system backwards; that is, by correlating the brightness of
    areas in the scene to the graph, you choose the correct negative
    density to obtain the effect you desire in the print. The graph tells
    you what camera settings to use and what development time to use. How
    do you know what density to pick? By printing a step-tablet negative
    with your usual paper and developer, you can determine what printing
    density is needed to obtain any shade of gray. The result is a
    negative that is optimized for your printing system, be it silver,
    platinum or any other negative/positive printing system.
    I can only summarize the system here but I encourage you to read
    the articles and see if it doesn't make better sense than the Zone
    system. If you do try the system, I'd like to hear your reactions
    and, of course, I'd be happy to answer your questions.
     
  8. A question rather than an answer, if I may, for Pete Andrews: What is
    the maximum Dmax for colour films like Velvia and Provia F
    with 'normal' exposure and development? I notice that some scanners
    are claimed to have a Dmax as high as 5.7.
    Thank you!
     
  9. Jason

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    As I have said before in this forum, too many zone system beginers
    get too hung up on the negative to the point where they forget that
    the negative is not the end product of the photographic process.
    Rather, it is the print, and we should test from the print back
    instead of from the negative back. (or, to put it another way, who
    cares if the density range is .20 to 500 or whatever, as long as
    whatever that density range is fits on the particular paper that we
    are using. So, before you get all worked up about densitometry, do
    yourself a favor and work with the best densitometer you will ever
    own, which is your two eyes.
    Take an unexposed but fully developed (film base plus fog) negative
    and do a maximum black for minimum time test. write everything down
    so you can duplicate it exactly. Now you have a basis from which to
    use your eyes to test what you need to know. then expose that zone 1
    negative and print it for the exact same time as your zone zero
    negative. see if you have a discernable difference. if not you need
    to expose more (make the negative more dense at zone 1. if too much
    expose less. Then, expose a couple of negatives for zone 9 and print
    them at the exact same time. see whether you need to develop longer
    or shorter to get just under paper base white. THEN, if you want to
    start measuring things with a densitomter you can do so. Youll get
    some numbers that may or may not help you. But the whole exercise of
    making negatives at the extreme ends of the paper, and really LOOKING
    at what happens there with your own two eyes will help you
    immesureably, and in my humble opinion much more than measuring those
    negatives with a densitometer. But remember, you have to establish a
    base from which you test everything, and then always test from that
    base so you have something to compare. And in my humble opinion,
    with black and white, the best thing to test from is maximum black
    for minimum time on the PAPER YOU ARE GOING TO USE TO PRINT WITH.

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    Good luck.

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    Kevin
     

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