Help with the Zone Systemgreenspun.com : LUSENET : Large format photography : One Thread
I am trying to evaluate Aristo ISO 125 8x10 film using the test procedures outlined by Ansel Adams in _The Negative_.
I am measuring densities with a Highland transmission densitometer.
My developer is Ilford ID-11 stock diluted 1:3 with distilled water.
I am getting a reading of 0.03 for film base + fog
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.
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.
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.
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.
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.
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.
I thought someone out there might have some insight into what I am doing wrong here.
Thanks for any information you can provide.
-- Jason Kefover (email@example.com), February 04, 2002
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).
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.
Hope this helps. Cheers, DJ.
-- N Dhananjay (firstname.lastname@example.org), February 04, 2002.
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.
-- Michael Feldman (email@example.com), February 04, 2002.
You raise a very important issue, the only place I've seen this addressed is in a book from Kodak.
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.
Your own measurement of this film shows that it cannot produce a density range of 2.4--it maxes out at nearly 2.
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.
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.
-- Charlie Strack (firstname.lastname@example.org), February 04, 2002.
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.)
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.
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.
-- neil poulsen (email@example.com), February 05, 2002.
I think you're confusing absolute density steps with the gamma corrected density 'zones' that you get on a negative.
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.
Your mistake has been to assume that the film should give you a 0.3D change in density for each zone change.
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.
If your negatives are in this region then they'll print OK, and that's what it's all about, isn't it?
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.
1) Why are you diluting ID-11 to 1+3?
2) To what purpose are you doing all this sentometric measurement?
-- Pete Andrews (firstname.lastname@example.org), February 05, 2002.
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.
-- Andy Eads (email@example.com), February 06, 2002.
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!
-- Julio Fernandez (firstname.lastname@example.org), February 07, 2002.
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.
-- Kevin Kolosky (email@example.com), February 07, 2002.