I am trying to learn how to develop and print all over again. My first step was to try to figure out my film speed. I'm using T-Max 400 in 4x5 sheets, developing in D-76 undiluted in a Unicolor drum that I rotate by hand. I am using T-Max because its reciprocity failure characteristics are much more merciful than Tri-X, and since I like depth of field, I am often shooting at f32 or f45.
For my first test, I found a smooth, dark surface, metered it, and underexposed it by 3, 4, 5 and 6 stops, pulling the slides out half-way. I figured that the first negative I saw the difference between the exposed and unexposed halves of the slide would give me a Zone I exposure and an approximation of film speed. This gave me an indication that 400 is a reasonable speed for this film, but I don't know whether I am really above the foot of the light curve for the film.
I tried printing that negative to get an idea of what the standard print exposure would be. I use an Omega D-2 condenser enlarger with a 135-mm El-Nikkor lens. A stepped-exposure print showed me the first difference between the exposed and unexposed portions of the negative at 24 seconds at f45. That seems very fast to me. I found a nice, contrasty subject to test this with yesterday. The film has been developed but I haven't had a chance to print it yet.
I saw a post here in which somebody mentioned using a home-made densitometer to check that his Zone I exposure was giving him a density of 0.11 above film base and fog. I strongly suspect that I don't have that much density. So, is there a way for someone with a simple darkroom setup to find out what Zone I should be? Or should I figure on spending a couple hundred dollars for a used densitometer on E-Bay?
Thanks very much!
Before I bought a densitometer, I had a commercial lab (not a one hour place) measure my film densities. The cost was minimal. To try to determine the difference of print tonality in the lower zones, as you are attempting, is going to be highly inaccurate. The reason is that those densities exist on the toe of the curve and are not well separated. I don't think that there are very many people that could tell a .10 density difference on a print tonal scale in the lower zones. Even metering through the negative would only define a 1/3 stop difference if the meter is truly linear and highly accurate.
Zone one density will be on the toe of the characteristic curve...that is as it should be. If you want to move your exposure up off the curve then you will need to make the proper zone placement at the time of the exposure. To do otherwise would be to assign an arbitrary and inaccurate film speed to the film. Let's say for instance in your case you decided that the Zone I density should actually exhibit as a Zone III print value, that would lead you to assign a 100 EI to your film (overexpose by two stops). That would then place your zone VIII and above values on the shoulder of most film's curves and then you would have some shadow separation and limited highlight separation.
I tried this: (like in the Hutchings book on PMK) A bright light at the top of a long white sheet. Then I metered all the zones with my spot meter and placed circles where those zones were. I then shot three sheets for each film I was testing. Each sheet got a different development time. I then printed them all on #2 paper with the developer I will use and choose the print that got all the zones. That way I have the development time that goes with the complete combination. If the sheet with the correct span of zones looses zone 1, I know to lower the film speed and re-shoot. I found that manufacture specs usually print at N+1 on grade 2 paper. So I usually find that nearly 1/2 ISO film rating and 15% off development time is close to where I will end up for N processing. I don't have a densitometer. I could probably tweek this a little more - but I am very close.
The film speed is connected to the contrast compression and contraction you want. So to determine film speed without contrast at the same time will not really get you where you want to go.
As I understand things, shadow densities should be used to determine film speed because changes in development time won't affect them significantly. A Zone II exposure will give the same density on the film whether it is developed for 80% of the standard time or 120%. Film speed is all I am trying to establish now.
I don't really understand your example of a Zone I density that I would want to exhibit as a Zone III print value. If I want a value to appear as Zone III on the print, I will ensure that it has Zone III density (whatever that turns out to be) on the negative. I would never intentionally try to make a Zone I area on a negative give me a Zone III area on the print. And if I have highlights that I am afraid will blow out, I will underdevelop the negative to keep them under control.
Although i agree w/ dnmilikan on taking your negs to a commercial lab for reading.
A quick read method is to purchase a Kodak .10 neutral denisty gel (2"X2"). Its the same density that is representative of a Zone I w/o film base + fog. You can visually match your Zone I neg by placeing the .10 gel over a clear (unexposed) negative and then matching that combination to the negatives you believe to be your Zone I neg.
My example was to illustrate that if one were to not accurately determine the Zone I density representing the actual film speed in your camera, lens system , and meter the tendency would be to arrive a too high a density for Zone I because it would be very rare that any of us could determine a .10 negative density difference in the lower zones as it prints on enlarging paper.
The difference between Dmax and .10 is something that I could not determine by visually determining it myself in a projection test. The net effect by the time one saw a difference on a projection test such as you described would be too great a density and that would have the effect that I described of raising the high values prematurely onto the shoulder region of the film. I hope that I have explained myself to your understanding.
I'm currently using a small white plastic sheet over the front of the lens (lens set at infinity) to get a uniform exposure. I used to use the grey card method, but find it difficult to get uniform light at times. The plastic sheet is practically foolproof. Ansel Adams talked about a "preexposure device" in The Print. It's just two plastic sheets instead of one with three sides to make a "pocket". Then you can get fancy and use ND gels with cardboard holders to control the light more.
For the measuring I bought a used color densitometer (X-Rite 810) from ebay for about $300US. It's indespensible IMO. Also be sure to buy a plaque and transmission reference. You'll need a way to zero out the unit initially and periodically thereafter. I measure for Zone I by finding the neg with a density between 0.10 and 0.15. When I make the test neg, I use twelve frames like so:
1) Zone I 2) +0.5 3) +1.0 4) +1.5, 5) +2.0, 6) Zone I
7) -0.5 8) -1.0 9) -1.5 10) -2.0 11) blank 12) Zone VIII
substitute 1/3rd stop increments instead of 1/2 if your lens can do that. Develop in you favorite soup (mine is PMK and Paterson FX-50 these days) and measure the negs. After Zone I is nailed, you can vary the dev time to try for Zone VIII (from 1.30 to 1.35). It can be tedious and I have burnt five or more rolls of film testing, but it pays dividends when you get your processing down pat. You will have to repeat the Zone VIII part over if you want to test for N+1 and N-1. I've never done it since it's a little more difficult with roll film, but it should be easy once you have your normal EI and dev time. BTW, the smiley face is supposed to be an eight follwoed by a parenthsis. Foiled by the emoticons... :-\