Questions about Zone System, EI and test data

[omiya_lee1]

I wanted to understand more about the Zone System. I read the

books ?The Negative? and ?The Prints? written by Ansel Adams and

some others who suggested using two-zone instead of ten. I have two

questions that I could not get an answer from the books I had read.

Here are the questions:

 

1. If N-1 (or N+1) is needed, do I need to also adjust the EI told

by the meter?

 

2. Since there are not many choices of film and developer available

today (as far as I know), Zone System users may use more or less the

same things. If I want to use the Zone System, do I need to start

from scratch and do all the tests first? Or, are there any

resources available with these data?

 

Thank you.

 

Omiya

[smieglitz]

Yes and Yes to your questions.

 

As you adjust your development to bring highlights into the proper zone, you will shift film speed slightly. In general, for each +1 stop increase in development, adjust your film speed higher by 1/3 stop before exposure. For example, expose TMAX 400 at EI 500 if you will give N+1 development. For N+2, rate the film at EI 640, etc. For contraction the same rule will generally hold. If N-1 development is to be given, rate the ISO 400 film at EI 320 and so on. Of course, one of the points of the film testing is to determine proper EI settings for various conditions and developments. You may find your personal results differ slightly from the recommendation I've given above as they are just generalities and not specific to your equipment and methods.

 

That leads into your second question. Because individual equipment, methods, and materials differ, you need to run the tests to determine your personal settings.

 

Having gone through all the testing several times I can also relate that one can approximate the results of ZS practice in general outdoor photography by simply noting the sky and shadow conditions and adjusting the EI and development accordingly. For example, on an overcast gray day with indistinct shadows, you may find yourself underexposing the film and overdeveloping it. In ZS terms you might be giving perhaps N+2 development and rating the 400 film at EI 250. On a bright sunny day with distinct hard-edged shadows you'll be overexposing (lowering EI) and underdeveloping (N- contraction development) to adjust contrast.

 

The big difference is the latter procedure does not take into account the subject values as ZS measurements would do. Also, they are just general guidelines for out-in-the-open situations and won't help if you are doing interiors or studio settings, photographing in deep woods or other low light conditions, etc. But, for a novice ZS worker the above may provide a quick reality check as to whether you are interpreting the scene correctly. For a hazy day, push (higher EI and increase development) and for a sunny day, pull(lower EI and decrease development).

[macgregor_anderson]

I'm not all that experienced myself with this stuff, but I have done some testing using visual guidelines as opposed to the more technical and accurate densitometer testing.

 

There is one concept that is important to understand and it may help you understand question number one.

 

The basic idea is that your shadow areas finish developing within a few minutes and that areas of the film that got lots of exposure continue to develop and get denser on the negative the longer you leave them in the developer.

 

Your film speed you select determines where you will have detail in the darkest areas of the scene. Zone III represents this threshold. No amount of developing can add detail here if you don't expose the film enough.

 

As you adjust your development times, that zone III stays almost constant. Progressively up the scale you get more and more development over time.

 

So in theory, the EI stays the same. However, small adjustments may be needed since there is some slight additional development over time in the shadow areas. And if you are looking to maintain zone V (middle grey) you will definitely need to adjust EI.

 

But if you expose for the shadows and develop for the highlights as they say, your shadows should stay pretty constant over a wide range of development times, and require very little if any adjustment to EI.

 

I'd suggest buying a step wedge and shooting say five sheets exposed to zone X with the wedge sandwiched above the film in the holder. Develop for a wide range of times, say 5,7,10,14,20 minutes. Contact print those wedges and see the change in various zones for yourself. It helped me understand a lot better how a scene might look with various development times at a constant EI.

 

Mac

[macgregor_anderson]

Joe, question for you. Does that 1/3 stop adjustment aim to keep middle values like zone V where they belong, or does zone III actually move that much? Since I don't have a densitometer and my test conditions aren't as constant as I'd like, I'm not sure I'd see a 1/3 stop move in the shadows with visual testing.

 

Like I said in the post above, I don't know a whole lot about this stuff myself.

 

Mac

[smieglitz]

Mac,

 

A couple clarifying points perhaps:

 

1. You said: "Your film speed you select determines where you will have detail in the darkest areas of the scene. Zone III represents this threshold." Actually, the EI/film speed point is based on Zone I in the ZS, not Zone III. Technically, the exposure threshold (where the film first responds to exposure) actually is below the value for zone I on the characteristic curve. Most ZS users look for a net density of 0.10 above filmbase-fog to define the speed point. Adjustments to development will shift the position of this point on the characteristic curve as I've stated in my previous answer.

 

If you were to take your several stepwedge tests and plot the data as a series of curves on the same sheet of graph paper, you would see the curves rise a bit in the shadow areas with extended developments even though shot at the same ISO so that the 0.10 net density point shifts to the left with increased development and therefore occurs at smaller effective EIs.

 

Most workers are concerned with getting full shadow detail in zone III, but that is not the basis on which their EIs are determined. Most would use the position of the 0.10 net density value as the determinant of EI. If that EI is used, chances are very good that zone III will always have significant detail and full texture if the visualization of zone III and the metering has been done properly.

 

2. You also asked: "Does that 1/3 stop adjustment aim to keep middle values like zone V where they belong, or does zone III actually move that much?" No is the answer to that question. The ISO shift aims to keep the value of zone I in place at a constant density value of 0.10 above fbf. The other zone values including zones III and V will drift both visually and with respect to their density values. However, the higher zones drift more than lower zones. In this respect, all the Zone System really is is a twist on the old adage "Expose for the shadows and develop for the highlights." Again if you plot the tests on the same sheet you will observe how the density range between any two zones increases at the same exposure level if you increase development. (For example at zone III exposure you will see a minor difference in density between the 5 minute curve and the 10 minute curve. But if you look at zone V, the density spread between the two curves is greater, and it is greater still at zone VI, and Zone IX, etc.)

 

3. One final point that is often overlooked in discussions of zone sytem and film testing: Just like you need to have some criterion for determining the effective EI (i.e., a net density of 0.10 above fbf at zone I vs. net density of 0.15 above fbf at zone I) you also need to define what the terms N+ or N- mean to you personally. Are you looking to raise zone V to the density of zone VI for N+1 development, or are you basing N+1 on the development shift from zone VII to Zone VIII? Those two cases will produce different development times and probably different EIs. The same holds true for contractions. Is N-2 from zone IX to VII or from Zone VIII to VI or VII to V? Each practitioner needs to define these criteria for themselves. That's why just following book recommendations often doesn't work and merely confuses.

 

The point of the zone system testing is to personalize film exposure and development methods for your own way of working. It is not to simply copy Adams, or White, or Schaeffer or Johnson or Bond or... It is however to get an individual eventually to the place where the technique becomes something almost entirely in the background and the concentration can be on the visual scene before them rather than on equipment or darkroom. A quick close read of Adams in "The Negative" reveals that he thought visualization was the key to the zone system and the most important thing to gain from it. He says so in the opening couple pages of "The Negative." All the other stuff is really secondary and has been taken and blown way out of proportion and overcomplicated. It really is just"expose for the shadows and develop for the highlights, and there are several ways to get there. The "systems" are just codified differently. Adams' Zone System is one, Davis' "Beyond the Zone System" another, and Kodak's (or Mortensen's) "ring-around" testing will all produce useful results.

[smieglitz]

"Does that 1/3 stop adjustment aim to keep middle values like zone V where they belong..."

 

Mac,

 

If you read "The New Zone System Manual" by White, Zakia, and Lorenz you will discover a discussion of technique where a middle zone stays fixed and the other zones fluctuate around it. They call this technique "Bi-Directional Contrast Control" IIRC. When I think of keeping a middle zone density constant like this, I think in terms of a seesaw with both ends rising and falling in opposition with changes of exposure and development. With different combinations of exposure and development, e.g., underexposure and overdevelopment vs. overexposure and underdevelopment, one can keep a constant density value for any single zone if desired. All the other zones will have widely different density values on the two films if compared.

 

OTOH, I envision the traditional Zone System practice as sort of "nailing down" the shadow end at Zone I and net density of 0.10 above fbf, and letting the mid and upper zones rise and fall in relation to this tethered shadow point as development is varied.

[macgregor_anderson]

Joe, thank you so much for taking the time to explain that. Sounds very familiar now that I think about it. I remember testing for threshold at just above pure black, or zone I as you said, not zone III. I got confused because I expose for zone III frequently. Hopefully I didn't confuse anyone with that mistake.

 

Omiya, hope I didn't divert your thread from your main focus. Seems that Joe has done a great job explaining how it all works.

 

One day I plan to do proper zone system testing with a densitometer. Since it's always a trade off between shooting more and learning in the field and testing time, I frequently don't get as far as I'd like with testing.

 

I will say, however, that I definitely benefitted from doing my own (rather casual) testing. Finding film speeds that saved shadows was a breeze. And the shifts apparent to the naked eye help a great deal in understanding development times. Since my first testing I've almost never been stuck with a negative that was so badly exposed I couldn't work it out in the darkroom. Protecting that shadow detail and not developing for waaaay too long has improved my exposures a great deal. Which lets me worry about my real issues...finding stuff I want to photograph and figuring out how I want it to be represented. I'd say even simple film speed testing and playing with development times in a controlled environment is well worth the trouble.

[smieglitz]

"Since I don't have a densitometer..."

 

Mac,

 

Purchase (for ~$9) a Stouffer 21-step density wedge (if that is not what you have already) and have the densities read by a local lab or ZS photographer. Record the density values for future use. This will give you a reference that you can visually compare your test films to and determine the densities achieved by different zones. The steps of the Stouffer wedge begin around a density of 0.04 for step 1 and increase by about 0.15 density per step (= one-half stop per step) all the way to around 3.0 for step 21. You might also invest in a Wratten #96 0.10 neutral density gel filter to use as a visual comparator for the zone I density target value. You'll be amazed how accurate your eye can be when comparing two film densities on a light table. Using two white index cards with a hole punched out of each and placing them over the respective film densities makes the comparison even more accurate.

[smieglitz]

I said: "In ZS terms you might be giving perhaps N+2 development and rating the 400 film at EI 250"

"

Oops. That should read ...400 film at EI 640..." for an N+2 development change on that foggy day. You want to underexpose and overdevelop in that situation. Sorry for any confusion.

 

Joe

[macgregor_anderson]

Joe, I had the pleasure yesterday of trying (and eventually succeeding) to jam that exact step wedge into my fidelity holder with a sheet of HP 5 already inserted. Those holders are still only a year old and fit pretty tight. I got it down finally and managed not to destroy the step wedge.

 

Took about an hour yesterday morning exposing at zone X on five sheets. Decided that I needed a sixth sheet of film in the mix, this one unexposed, to aid in finding my contact printing time. Of course a few minutes after I added it to the bag of exposed film I realised that I had no idea which was the unexposed sheet and which were the identically exposed step wedge sheets. Makes it kinda hard to stagger development. I briefly considered developing one at a time for a minute or two to find the blank sheet, hopefully saving a few shots. Instead, I swore and scared the cat, threw the sheets down in the bathroom (toilet cover up, so a couple had to be fished out of there later). And started over.

 

I got four sheets exposed (wanted five) and figured out a way to stagger development in my brand new combi tank. Without throwing off the normal aggitation method, or adding in any pouring time errors, etc. I had been using trays and no matter how hard I tried I couldn't control aggitation. Just shuffled too fast in the dark. Very contrasty negs from that. Well, the Combi tank worked great for me, and I've got four HP5 step wedges developed for five, eight, 11, and 14 minutes. Not gonna find N+2 with that, but I rarely want it, and besides, I'll probably fine tune later.

 

It was a frustrating day, but also time well spent. I tested HP5 before, but not using the Combi. And I forgot where I put the notes.

 

Omiya, don't let it scare you off testing. You would have to try very hard to screw this up as badly as I have. And even I got valuable info in the end.

[huw_finney]

With modern films and their lattitude combined with VC papers I meter for the shadows using the stock EI and eyeball the contrast. I end up with 3 boxes to develop, one at the recomended time, one -30% and one +50%. Works for me.