Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Zone System Question - Help Me Out

  1. #1

    Zone System Question - Help Me Out

    I am interested in determining if there is a mathematical correlation to determine the correct reflection densities of a nine zone range with Zone V (18% grey card) as middle grey. As a point of reference, I am getting a reflection density of 0.81 for Zone V.

    My reference department is lacking in this department. My thanks in advance.

  2. #2

    Zone System Question - Help Me Out

    Zone to zone is 0.3 density difference. I always use transmission densities of the negative to determine what's right or wrong with assumtpion that a density of 0.1 above film base + fog is Zone I. The above is based on the fact that in order to have ANY texture recorded in Zone I you must expose it to just above what film base + fog would be, which varies from film to film. Then a 0.3 difference doubles the exposue or takes you to the next zone up.

    That is of course a starting point which you can then alter to your liking.

    From above, if you add density of the film base + fog to your gray card reflection of 0.81 you should be getting a fairly close figure to what you should expect from a Zone V transimssion density of your negative. Ensure that your instruments are well calibrated, or at least have a consistent correction factor, so your readings are something you can trust.
    Witold
    simplest solutions are usually the most difficult ...

  3. #3

    Join Date
    Sep 2003
    Posts
    1,545

    Zone System Question - Help Me Out

    As I understand your question you are wanting to work up a correlation based on reflection densities using Zone V reflectance as the benchmark. I would need to answer no unless you want this for only a given paper/grade. I suppose that one could come up with the curve for a given paper and contrast grade. To do that I would contact print a calibrated step tablet on the film that I was using. I would then take that film negative and contact print it on the paper that I was using and read the reflection densities of each step. This would take into account the film characteristic curve and also the papers characteristic curve. Zone transmission densities are not linear .30 as they are represented on film. This belief disregards the characteristic curve of the film.

  4. #4

    Zone System Question - Help Me Out

    Transimission densities are represented by logarithmic values, not linear. If the question here is with regard to getting a zone 5 in print FROM film then film density to get that value will have to be taken into account anyway.

    Above values I've given come from well regarded publications.
    Witold
    simplest solutions are usually the most difficult ...

  5. #5

    Join Date
    Sep 2003
    Location
    Kalamazoo
    Posts
    648

    Zone System Question - Help Me Out

    I would think there is a mathematical function that describes this, but I'm not sure where you'd find the information. I suspect searching/googling for psychophysiologic tests might turn up the answer somewhere. What you are seeking sounds like data on psychophysical response of the human visual system. You have a reference point, 18% gray reflectance, that is producing a subjective interpretation of "middle gray" halfway between black and white. That's quite a bit different than the visual effect a 50% gray produces.

    If you could find or produce the tones that represent the various tones you interpret to be the different zones and measure them yourself, I would think that might provide more useful information to you than some table of numbers measured on a different material and application. In other words, a 36% gray might not be Zone VI for you but if you had a printed tone on the paper you normally use that gave you your own subjective Zone VI value, the reflection of that sample might be better applied to your own photographic practice.

    Having speculated above I can also relate some reflection data from the gray scales patches in an old 1975 Kodak Professional Dataguide. They aren't "Zones", but are close:

    step , Reflection , R Density , subject:

    1, 84%, .08, whitest snow & clouds;

    2, 42%, .38, white sand/white paint;

    3, 21% , .68, Caucasian skin/light grass & foliage/deep sky/wet white sand/weathered wood;

    (gray card, .78, 18%, gray side of a Kodak gray card);

    4, 10.5%, .98, dark skin/foliage/earth/dark tree trunks;

    5, 5.2%, 1.28, black fresh turned earth/dark clothes;

    6, 2.6%, 1.58 most black objects;

    7, 1.3%, 1.88 blackest objects;

    8, 0.6%, 2.18, black velvet;



    Hope this is what you are looking for,

    Joe

  6. #6

    Zone System Question - Help Me Out

    There is a mathematical basis but you will have to define what the zones mean and have reflection density values for the black and white end tones in the scale. Then simple proportion determines the reflection density of any zone. If in your example we presume that Zone V in the print is the mid-point tone between black and white, then the reflection density would be:

    Zone V Density = Dlow + 0.5 * Dfullrange

    where
    Dlow = Dwhite + 0.04
    Dhigh = 0.9 * Dmax
    Dfullrange = Dhigh - Dlow

    where
    Dwhite = reflection density of unexposed developed paper
    Dmax = reflection density of completely exposed developed paper

    Using the typical values for the above variables and your 0.81 figure, we could work backwards and say that the Dfullrange would be 1.40 and that Dmax is 1.67.

    0.81 - 0.11 = 0.70 (Dlow)
    0.70 * 2 = 1.40 (Dfullrange)
    (1.40 + 0.11) / 0.9 = 1.67 (Dmax)

    A Dmax of 1.67 and Dfullrange of 1.40 for photographic paper is a bit weak. It sounds more like the values for an ink print.

    If your Zone V is something other than the midpoint, use simple proportion to determine its place on the Dfullrange scale. (Notice the 0.5 multiplier in the first formula. It could also be 0.4, 0.6, etc. for other proportions.)

    Dlow and Dhigh definitions are based on an ANSI standard test method. Using simple proportion presumes a linear relationship on a log-log scale between density and zone. This method is commonly accepted but other schemes using a non-linear relationship between density and zone could also be used.

  7. #7

    Zone System Question - Help Me Out

    oops...

    0.81 - 0.11(Dlow) = 0.70 (midpoint of Dfullrange)

  8. #8

    Zone System Question - Help Me Out

    I have to say that 0.04 of density increase is not enough though. This is a kind of texture that may be noticeable under a magnifier yet, we're looking for a visible details with a naked eye. As Ansel and others suggested, the 0.1 above film base + fog is I think a more realistic figure.

    While densities are given in logarithmic values, the film or paper response curve is mostly a straight line. It bends below zone 3 and above zone 7 (an approximation). A simple linear ratio should work just fine.

    Again, I would work on the negatives to get the zones-by-densities first. Then do the printing and alter my zone definitions as needed.

    I usually see little value in extensive testing of paper as the image itself may require a different approach and I may want to depress some detail in shadows or highlights. However, I do believe in having the detail available to me at time of printing. It is thus more important to test the film and what I need to do to expose it correctly.
    Witold
    simplest solutions are usually the most difficult ...

  9. #9

    Zone System Question - Help Me Out

    Mr. Grabiec, I could be mistaken but I believe that Mr. Kadillak is asking about reflection density of the paper rather than transmission denisty of film. Log 0.04 above white (b+f) is a reflection value used in the ANSI and ISO standards for determining the white end of the density range of paper. Did I misunderstand the question?

  10. #10

    Zone System Question - Help Me Out

    I think you're fine Mr. Poinsett. And you're right about that other end of it. As I mentioned in my post the negative is the key to what I believe in, but I'm quite confident that a 0.04 density difference from a WHITE paper base, will be a hard sell for viewers. I may be wrong though.

    I realize I may not have been unswering the actual question, yet there is always a correlation between the two, to me anyway.
    Witold
    simplest solutions are usually the most difficult ...

Similar Threads

  1. Zone System Exposure Question
    By scott jones in forum Style & Technique
    Replies: 7
    Last Post: 25-Feb-2002, 09:56
  2. Zone System Question
    By howard s in forum Style & Technique
    Replies: 9
    Last Post: 22-Jan-2002, 20:23
  3. zone dial or zone system wheel
    By jerry smithson in forum Style & Technique
    Replies: 3
    Last Post: 13-Apr-2001, 18:19
  4. ZONE SYSTEM
    By Martin_1505 in forum Style & Technique
    Replies: 7
    Last Post: 24-Jan-2001, 08:29
  5. Zone System: Zone 7 or Zone 8 for Highlight Testing
    By William Marderness in forum Style & Technique
    Replies: 5
    Last Post: 14-Feb-2000, 10:50

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •