Please Explain: Density Ranges

[Richard Ryerson]

Hello all!

First off let me apologize for posting this question. I know this subject has been beaten to death, but I can't seem to get a foothold. Also, please excuse me for posting in a large format forum when I shoot 35mm & 6x6.

I am having trouble figuring out negative densities. I am not looking for a magic bullet, however I am trying to reach a level of understanding where I can remove unknown variables, by making them known and controllable, that way I can focus on other areas that I need too, such as composition and the likes. (I am a left brain personal so I lean towards the technical aspects of a problem first)

Before I pose questions let me explain what I do understand about the Zone System and negative densities.

I understand the zone system to be a technique/method to expose, develop and print photographs. It encompasses various variables such as development temperature and time to produce predictable results using consistent techniques and equipment. (How’s that for generalization?)

For a simplistic example: I expose an 18% gray card at the settings my meter advises me to and I will get a Zone V density in the negative when I develop the film under my personal normal development procedures.

Similarly I will get a Zone VIII density in the negative when I open the lens up 3 stops from the meter reading for the same 18% gray card, in the same lighting conditions.

Hey that’s easy to understand. Sounds great to me, I can eliminate some variables and focus elsewhere besides a bracket until you vomit technique.

Now if each Zone represented in the Zone System corresponds to a doubling or halving of light from the adjacent zone and Zone 0 is a 0 density (or equal to FB+F) and each doubling or halving of the log value of opacity (density) is +/- .3 from the adjacent zone density, I should expect a zone density of 1.5 for the Zone V exposure and a zone density of 2.4 for the Zone VIII exposure. And for the speed value zone, Zone I, we are looking for a zone density of .3. These values are densities above FB+F.

You can probably see where my first question is going to be. If the targets of the Zone I, V and VIII exposures are “supposed” to be .3, 1.5 and 2.4 respectively; why is it everyone always talks about targeting .1, .6 and 1.15 over FB+F?

I had the thought that it may have to do with the range of the film / developer / time combination. We have 11 zones to place into a density range.

That leads me to another question. If DMax and DRange are based upon development time (leaving everything else the same) how are we supposed to determine the normal development time, if DMax and DRange change due to development time?

Let me try an example just to hash out this problem:

Example A:
DMax: 1.44
DMin: 0.02
DRange: 1.42
Dev: D-76 1:1
Time: 9:30

Zone 0 Negative Density = 0.02 = DMin
Zone 1 Negative Density = 0.16
Zone V Negative Density = 0.73
Zone VIII Negative Density = 1.16
Zone X Negative Density = 1.44 = DMax

These theoretical values based on placing 11 zones into DRange would be altered if I changed the development time. Let’s pretend that an increase to development time of 25% would increase the DMax by 25%.

Example B:
DMax: 1.8
DMin: 0.02
DRange: 1.78
Dev: D-76 1:1
Time: 11:53

Zone 0 Negative Density = 0.02 = DMin
Zone 1 Negative Density = 0.198
Zone V Negative Density = 0.92
Zone VIII Negative Density = 1.444
Zone X Negative Density = 1.78 = DMax

Now of course this affect is to be quite desirable when we are expanding and contracting the contrast of an exposure in the ‘real’ world. But before we can expand and contract we must determine the proper development time by exposing a Zone VIII exposure and checking the density. But what are we checking against? Since both of the above two examples differ from the 2.4 density expected for Zone VIII, which one is right?

And if each zone represents a halving or doubling of light from the previous zone, why is this not the case in targeting densities?

Thanks for all your considerations here. I know this must be pretty nit-picky, but I need to know where to begin.

Best regards,

Rick

[Bruce Watson]

Now if each Zone represented in the Zone System corresponds to a doubling or halving of light from the adjacent zone and Zone 0 is a 0 density (or equal to FB+F) and each doubling or halving of the log value of opacity (density) is +/- .3 from the adjacent zone density, I should expect a zone density of 1.5 for the Zone V exposure and a zone density of 2.4 for the Zone VIII exposure.

I think you are confusing the subject brightness range (SBR) which is light (and zone-to-zone changes which can be thought of as a doubling/halving of light), with the film densities. The two aren't the same, but are related though the film's gamma (contrast index) which is a characteristic of the film and which one can modify through developement. IOW, it's not reasonable to expect to get a zone-to-zone density change of .3. This will seldom if ever happen.

For example, a more resonable expectation for densities would be for Zone I to be .1 over filmbase + fog, and for zone VIII to be around 1.3 (this will vary depending on what equipment you entend to use to print). A zone VIII value of 2.4 would be a seriously cooked negative.

I second Ken's recommendation of Picker's Zone VI Workshop which gives a fairly easy to understand explanation. Adams' book The Negative gives a more in depth explanation. I'm sure there are other sources.

[Jorge Gasteazoro]

Richard, the answer lies in the cability that reproduction materials have to represent the tones. Most reproductions materials ( silver paper, glossy printing paper, etc) have an exposure scale or tone reproduction ability of only 5 stops. So while a negative is capable of capturing 10 stops (I am talking about B&W, color is a different beast) papers are only able to "fit" five of those stops in most cases, so we have to "tailor" the negative tonality to fit the reproducing material.

Of course there are some exceptions, but nevertheless most reproducing materials exhibit a compression of tones. Azo paper exhibits very little compression in tone reproduction and alternative printing methods exhibit a very large compression of tones in the low ranges but have great separation in the high ranges. A very good explanation can be found in the book by the late Dr. Henry "Controls in Black and White."

I hope this helped, good luck.

[Neal Shields]

I can't tell you how many books I had to read to even come close to understanding all this.

Sometimes I need to read one thing explained several different ways before I grasp it.

One of the problems that I had is there are 10 zones in some discriptions and more in others. I think that in his article series: Photographic Myths, Bruce Barnbahm says B&W film can capture as many as 16 doublings of light (zones) usefully. The Negative says that Zone 1 is pure black and zone 10 is pure white. Seemingly a conflict here.

I would add to the above recomendations:

Basic Photographic Materials and Processes (especially for someone "left brained".)

And Post Exposure by Ctein.

[John Cook]

Ansel Adams had the right idea, but couldn’t seem to spit it out in a manner that anyone could understand. He spawned an entire industry of people writing books and giving seminars, all purporting to explain what he really meant to say. These people have made such a mess of the subject, I’m not surprised you are confused.

Your post is okay until the paragraph beginning with, “Now if each zone”. The densities you state would only be correct if your H&D curve was a perfect 45-degree straight line, in which each unit of exposure resulted in a corresponding unit of negative density. Such a curve would be an accurate representation of reality.

But negatives need to be flatter than “reality” because print paper is very contrasty. Put a piece of paper in a film holder and shoot a landscape. The result, developed in print developer will illustrate the extent of this contrast.

In my personal case (may not work exactly for you) I need to have a negative with a Zone VII density of 0.8 (over bd+f) to get a perfect print (to my taste) with my Omega D5 condenser enlarger, lens, paper, developer, etc.

Draw a straight line from Zone I at 0.1 over bd+f to Zone VII at 0.8 over bd+f and you will see my “ideal” negative H&D curve. For other zone densities in between, you can look at the line and interpolate.

The second half of your question has my head spinning. I simply increase exposure until my Zone I is 0.1 over bd+f. Then I adjust development to get Zone VIII at 0.8 over bd+f.

Dmax, as I understand the term, only happens when I develop a piece of film or paper which has been exposed to room light and all the silver coating turns black.

As for the eleven stops, that’s where Ansel and I part company. I was trained among the old-time (early 20th Century) Hollywood cinema boys who followed Edward Weston’s ideas. (That’s Ed Weston the exposure meter guy, not Ed Weston the f64 nude green pepper guy.) We were taught that there are only 7 zones in b&w.

Measured with an incident meter, that’s a two stop or 1 to 4 lighting ratio. The sun giving off three times the light of the sky when conditions are perfect for b&w photography. One unit from the sky plus three from the sun means that the highlight side (total of four units) is two stops brighter than the open shadow side, which receives only the one unit.

Any more than that, and out came the fill cards, syncro-sunlight flashbulbs or taffeta overhead scrims. Or we all went home and waited for the “Magic Hour”, near sunrise or sunset. Any less than that and the diesel generator truck and Mole Richardson Key Lights were fired up.

That’s why old b&w movies look so nice. ;0)

[paulr]

"The zones are a contrivance to help visualize what would be considered 'normal' tones and give them a number, much like a mnumonic. Or so that is how I understand it."

This is exactly right. All of this is a contrivance, and the purpose of it is to make exposure and development control EASIER. As soon as it makes your life more complicated than it needs to be, take it as a sign that you might be drinking too much of the wrong kool aid. Don't get me wrong--the zone system (or any system) can be valuable to learn, but you don't need to understand every detail of sensitometry to use it. You just need a conceptual framework (so it all makes sense) and then whatever techniques actually serve your work.

Personally, I learned all the details, like a good geek, but then ended up discarding most of it. What serves my work is an extremely pared down version of the zone system--one that's fast, and at least for me, pretty foolproof.

Keep in mind that Ansel didn't invent variable exposure and development--he just invented a conceptual vocabulary for making it easier to teach and to understand. Remembering this goal (as opposed to tying to become a sensitometry technician) will help keep the process in the service of your work, and not the other way around.

[Richard Ryerson]

Thanks for all your excellent replies. They have all be very helpful. And thanks for not beating me up about shooting the 'lesser' formats.

I guess the gist the original question(s) were to understand how and why a value X was chosen to be good for a given zone. It seems to me that the answer lies within gamma / contrast index. That is totally reasonable to me. And I can sleep at night knowing why someone would say, "shoot for .8 above FB+F for Zone VIII." Without the generic answer because it looks good.

Thanks a million,

Rick

[paulr]

"As for the eleven stops, that’s where Ansel and I part company. I was trained among the old-time (early 20th Century) Hollywood cinema boys who followed Edward Weston’s ideas. (That’s Ed Weston the exposure meter guy, not Ed Weston the f64 nude green pepper guy.) We were taught that there are only 7 zones in b&w."

This is a perfect example of how the whole system is a contrivance and not a rigid product of natural law. The materials are very flexible; within reason you could have anywhere from just a few zones to close to 20. I believe 10 1-stop zones was chosen because it's a nice, easy number to work with, and because it corresponds pretty well to the degree of contrast it takes to make an average scene use roughly the full density range of a medium contrast piece of photo paper.

If you calibrated your process to give you 15 zones (which might involve using POTA or some other extreme low contrast developer) your negatives would be very soft, unless you were routinely photographing subjects with an extreme contrast range. Calibrating for 7 zones will likewise give you contrastier film. It would be appropriate for using softer paper, or else for photographing subjects with lower contrast ranges that you wanted to exaggerate. But most people, out of convenience, habbit, or because it just seems to work well most of the time, use 10.

For those times when fewer or more zones seem appropriate, we have all the ways of exoposing and developing for N- and N+ results. These are just techniques for adding and subtracting zones, which can be thought of as a simple description for changing the gamma.