Photographer's judgement is needed doing the tests. I don't think reflection densitometry of paper is much help due to the myriad of things that can distort reflection densitometer dmax readings.
Picker's book offers a send-in transmission densitometer test for 0.1 log D of film. There is no similar offer to perform reflection densitometry of one's maximum black test.
Zero a densitometer to Zone 0 makes not much sense. Zone 0 has no definition in ISO, or is it defined anywhere in the technical literature.
Standard practice is to null the densitometer to film base of the same piece of film on which one will make the densith reading.
The point of zeroing out the densitometer on a clear area of developed film is to remove the base + fog density. And, by definition, a clear piece of developed film is Zone 0.Originally Posted by ic-racer
Exactly how I have done it -- but I keep my ISO and development the same, so I only have to do it once for each type of film.
You seem to have a quite high base density at .29, so only about 1.00 overall between your hypothetical target points. But that's the second problem, it's still all hypothetically Zone this or Zone that. Not until you make real world exposures and see how they actually print will this begin to gel. Trying to overthink it all in advance using a step wedge might land you somewhere in the ballpark, but isn't quite the same thing. I'm not against densitometers - I've spent many many hours plotting actual curves with them. But until you've secured a working marriage between specific film protocol and a specific paper protocol, it's going to remain somewhat ethereal.
Exactly -- see "Controls in Black and White Photography" by Richard Henry -- do your own tests. How you expose and develop film depends on what paper you are using -- and how you expose and develop it. Start by figuring out how to develop the paper first, and then determine the range of the paper -- using a step table, of course. Then expose and develop the film to match -- not vice-versa.
And do your own tests. You are the prosecutor, defense attorney, judge and jury.
Last edited by xkaes; 5-Apr-2022 at 12:46.
Versus being presumptuous enough to "instruct" others how to proceed, I will instead relate my own procedure. And before doing that, let me point out that Ansel Adam's Zone System procedure was quite different from that which is typically applied today. For example, it was quite different from what John Sexton practices. So, I'm careful about taking values that Ansel Adams relates in his books too literally.
As to your question, I DO NOT subtract film base plus fog from densities that produce this or that zone on photographic paper. I want THE film density value that produces this or that Zone VIII or Zone VII exposure, and film base plus fog contributes to that density.
And, versus using someone else's density, I want THAT density that yields a Zone VIII that I like. (Not that someone else likes.)
But before I can do that, I need to know how long to expose the paper. That exposure becomes the minimum exposure that will cause a Zone 0 negative to print maximum black on my paper of choice. (Ilford VC WarmTone.)
But before I can create a Zone 0 negative, I need to determine the actual film speed of my film of choice. (Ilford HP5.) I establish film speed by determining the ASA that renders a Zone 0 exposure density that is 0.1 density units above film base plus fog after developing the film at the manufacturer's recommended time and temperature. So, it's only to determine film speed that we subtract film base plus fog. And, we obtain a Zone 0 exposure by taking a light reading of a surface, and then selecting a shutter speed/f-stop combination that makes that surface five stops darker.
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In reverse order, I first determine the film speed of my film. Invariably, it tests out at half the manufacturer's recommended ASA, which would be ASA 200 for HP5. (Since Ilford recommends shooting HP5 at ASA 400.)
Knowing the film speed, I can create a Zone 0 negative by photographing a homogeneous, flat, light gray surface using an exposure that's five stops darker than that recommended by the light meter.
Next, I can use that Zone 0 negative to determine the minimum enlarger exposure needed to produce maximum black on my paper of choice. There are different ways to determine when one has reached maximum black on the paper. Basically, it becomes a judgement call.
Once I determine the enlarger exposure time, then I can produce a Zone VIII negative, and see how light or dark it prints on my paper of choice. Of course, I will need to pick a time at which to develop that negative. So, what is called the "Normal Development Time" is that development time that renders a Zone VIII negative that prints a Zone VIII shade of gray that you like on your paper of choice. By selecting a Normal Development Time that you like, you have tailored the Zone System to your needs, versus to someone else's needs. Note that I always develop paper in Dektol 1:1 for three minutes at 70 degrees with no VC color filtration. I'm sure you have your own preferences in this regard. What's important is to always use the same development time at the same temperature.
For myself, I use that process to pick a Zone VII negative that I like, versus a Zone VIII negative. I find that a negative with density of 1.35 density units prints a Zone VII shade of gray that I like on my paper of choice. So, I select a Normal Development Time that gives me a Zone VII negative with a density of 1.35 density units. (The longer the Normal Development Time, the higher the density.) Coincidentally, this is very close to the negative density that John Sexton likes for rendering a Zone VII density. (At least, liked at the time that I attended his workshop.)
Last edited by neil poulsen; 5-Apr-2022 at 13:35.
Indeed a slope (contrast) yields the same result if one includes film base in the readings or not.
Of course speed determination, by definition, is independent of film base density.
As mentioned previously, there is no film rating system based on Zone 0, though, there is no law that says one can't make up whatever they want and post about it.
It was probably already answered, but you want net density, i.e 1.32 minus 0.29, the latter of which is quite high, by the way. That gives 1.03. For me, that's too low. I prefer a net density of about 1.25-1.3 for my Zone VIII.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
When I taught sensitometry, we would compare the Ansel Adams, Fred Picker (super simplified Adams approach) and The Beyond the Zone System methods by Phil Davis. FWIW, the variations in readings from a white card when used for determining development time and the number of variables can lead to some significant variations. Picker made a career out of special meter modifications to combat some of these issues as an example. Now, that said, the fastest and most reliable method were always the BTZS tests using a densitometer, stepwedge and controlled development. Among a typical class of 10-15 students, it was common to find a 30% variation (about one N number for Zonies) in development times using the white card and meter method. On the other hand, variations with the step wedge and BTZS methods were often less than 10% and the variation was always traced to agitation variations as all other variables (dilution, temps, etc) remained the same.
Just a thought....
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