Exposing a gray scale for Zone System calibration

[TroyG]

Hello, all!

I just got access to a darkroom so I am going to start doing my first round of zone system calibrations. As one of the final steps, Brian Lav suggests making a gray scale using your process for future reference. Rather than blow through 10 sheets of film would it be safe to do the following:

Set up a gray card and meter for a zone 1 exposure. Pull my dark slide out 1/10th of the way and expose. Pull it out 1/10th more of the way and expose again. Continue until you have (in theory) a 10-step grayscale. Does that work how I think it will? Because the first step got exposed to a zone 1 exposure ten times, does that make it Zone X?

Thanks, y'all!

[Christopher Barrett]

Not really. Your first increment will have a one stop difference but all of the subsequent steps will have smaller and smaller separations. With a base exposure of 1 second your strip would look like this...

1s / 2s / 3s / 4s / 5s / 6s / 7s / 8s / 9s / 10s

But to have 1 stop increments you would want something more like...

1s / 2s / 4s / 8s / 16s / 32s / 64s / 128s / 256s / 512s Now this isn't precisely correct because exposures shift logarithmically, but it should be fairly close. You can see how this changes things pretty dramatically. Also, just to get at these exposures requires even more math to figure out the cumulative final exposure times per step. Oh my head...

I'm assuming your greyscale strip should have 1 stop increments, yeah? Someone please correct me, if my logic is faulty.

-CB

[TroyG]

I believe the saying is "duh!". Thanks for pointing that out. I guess 10 sheets of film is cheaper than buying a broadcast chip chart of a gray scale. I'm glad someone stopped me before I was standing with a print in my hands shouting "do'oh!"

[neil poulsen]

How people do calibrations vary. (O course.) So, I can offer come comments based on my own approach.

Let's assume that you've completed your calibrations and know the following:

1] Tested film speed. (Usually about half the manufacturer stated speed.)

2] Determine paper maximum black for the paper of choice. (In my case, Ilford Warmtone fiber.) That is, determine the minimum exposure that maximizes black at whatever enlarger height, enlarger lens aperture setting, and light intensity, when exposed through a film-base plus fog negative. (I develop a negative that hasn't been exposed to light at mfg. recommended development time and temperature.) For maximum black, I determine that minimum exposure time that maximizes paper black through that negative. (But no greater.)

3] Normal "N" development time.

Knowing these, to get my Zone System gray scale, I would expose negatives respectively to light at Zones I, II, III, IV, V, VI, VII, VIII, and IX, develop each at Normal development, and print each of these negatives on nine sheets of about 4x5" paper at maximum black. This give one an idea of how each zone will print in the final print, when the negative is exposed normally

To construct the actual scale, I would trim each paper to about 1"x1.5" and mount these rectangles in order (Zone I through Zone IX) side by side on a strip of museum rag, four-ply mounting board with dimensions 9"x1.5".

As a caveat, I hear people say t hat a Zone V exposure should be about 68% gray. (Or, whatever.) It doesn't work out that way for me, and it doesn't really matter if it doesn't.

[xkaes]

I agree -- you can't expose film in a vacuum. You need to determine what comes AFTER the film exposure FIRST.



Check out: http://www.subclub.org/darkroom/henry1.htm

[Doremus Scudder]

Early on, I made Zone Rulers (Minor White's moniker for what you're doing) for all my different development schemes. It helped a lot in learning visualization of tones, especially for the expansions and contractions where Zone V is usually not anywhere close to 18% grey. Each development scheme has its own "scale" of greys and different intervals between the patches.

I expose two sheets of film divided into fifths or sixths (depending on how many stripes I need). Here's my method for nine stripes plus a strip of fb+fog.

First, I insert the darkslide 1/5th of the way (for the unexposed stripe) and make an exposure at Zone I. Then the slide is pushed in another 1/5th and I repeat that Zone I exposure (results in Zone II on the film). Insert the slide another 5th of the way and open one stop for the next exposure (Zone III on the film). Repeat that last step for the next stripe, i.e., insert slide, open one stop and expose (Zone IV on the film). That uses the first sheet for five stripes: Fb+fog and Zones I-IV.

For the next sheet, pull the darkslide completely and expose for Zone V. Insert the darkslide 1/5th of the way and repeat that same exposure (results in Zone VI on the film). Next, insert the darkslide, open one stop and expose (for Zone VII). Repeat this last step (insert and open one stop) for the next two stripes (Zones VIII and IX). The second sheet has five stripes, Zones V-IX.

The developed sheets get printed (I enlarge them to take enlarger flare into account because I enlarge; if you contact print, then contact print your negs) at "proper proof" exposure, i.e., minimum exposure to reach acceptable max-black from the fb+fog stripe. Then you can easily see where all the Zones fall and tweak your development scheme(s) as needed to get Zones III and whatever target Zone you're using for highlights in the place you want them.

Keep in mind, that this test doesn't reproduce a scene with many different luminances exactly, but it'll get you in the ballpark. Keep good field notes and adjust as needed.

And, as xkaes points out, you really need to kind of standardize on paper and paper development before making your Zone Rulers. Plus, film speed will change ever so slightly with different developing times, so you may want to repeat a particular ruler at a different E.I. if you need to refine the shadow values.

Best,

Doremus

[faberryman]

Dare I mention reciprocity failure in calculating the exposures?

[Jac@stafford.net]

Permit dissent. The Zone System today is a wasteful distraction
Can elaborate.
.

[Greg]

If you are interested in the Zone System, I'd suggest 2 books:
Photography: CONTROL & CREATIVITY by TL Bollman & GE DeWolfe
handbook for Contemporary Photography by Arnold Gassan

If you are really interested in the Zone System in depth:
Beyond the Zone System by Phil Davis

If you are historically interested in the Zone System
ZONE SYSTEM MANUAL by Minor White

Personally have been shooting B&W film, processing it in Diafine, and making digital negatives to contact print from with Platinum/Palladium, Salt, or Fiber base "conventional" paper. Really only now use the Zone System for determine exposure, but having done the complete Zone Testing several times over the years, what I learned still greatly effects my photography. If for any other reason, learning the Zone system allows photographers to converse with each other using a common language of tonalities.

just my 2 cents....

[Greg]

Permit dissent. The Zone System today is a wasteful distraction
Can elaborate.
.

Please do....