Help with the Zone System

[jason l.]

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

[dhananjay_n]

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.

[michael_feldman1]

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.

[charlie_strack]

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.

[neil_poulsen1]

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.

[pete_andrews]

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?

[andy_eads]

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.

[julio_fernandez1]

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!

[kevin_kolosky]

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