Zone system "System film-development time"

[henk@apug]

Hello,
I'm in the process of calibrating for the zone system. The first part of defining
the system-speed number is done through measuring density. The second part of defining the system film-development time is done through measuring
of density as well, but what I find a bit odd is that the density off the blank frame has to be added with 1.05 for a diffusion enlarger and 0.8 for a condensor enlarger (zone VII) This informtion I have from the Kodak Advanced B&W Photography book.
Is this correct for all sorts of diffuser/condensor enlargers ??
I have a Kaiser system V which is defined as a diffuser/condensor combination. What factor should I apply ?

Are there other ways to define the system film-developmnet time correctly
without using these factors ?

Thanks

 

[chriscrawfordphoto]

Condenser enlargers print with higher contrast than diffusion enlargers, which is why the negatives for printing on condenser systems need to be lower in contrast. There are differences between enlargers though, so really you need to test for your enlarger to get a dev. time that works to print your negatives on it.

 

[seadrive]

I wouldn't get too caught up in the exact density of a Zone I negative for condenser vs. diffusion light sources. If you start with one, and later switch to the other, what are going to do? Throw out all your negatives that were calibrated for the other type of enlarger? I don't think so, either.

Some (very well-known) photographers will tell you that testing film is a complete waste of time. Maybe they're right, maybe not.

But if you're going to do film speed and/or development time tests, here is (IMHO) the single most important piece of information you need to have: MTFMB.

That's the Minimum Time For the Maximum Black (a term first coined by the late Fred Picker) that the paper you're using is capable of delivering. It's the minimum exposure time that renders the maximum black of the paper when exposed through an unexposed, developed piece of film. It's the exposure time where all exposures of greater duration produce a tone no darker than the one produced at that time, through an unexposed, developed piece of film. The density of that negative is what's called "Film Base + Fog".

At the MTFMB, all negative densities greater than FB+F will appear as a shade of gray that is lighter than the paper's deepest black; from what we refer to as Zone I, all the way through Zone VIII, which (if your development time is correct) will be rendered as a shade of gray, just slightly darker than the base white of the paper.

If you do a test to find the Exposure Index at which the developed film's density is 1.0 over FB+F, but at MTFMB, you can't see the difference between that tone and pure black, then what have you gained? It's what the paper shows that matters, not what the densitometer says.

Use a strip of unexposed, developed film to find your MTFMB, then take some pictures and develop the film. Expose negatives under your enlarger for the MTFMB. If you have no shadow detail where you expected it, then you need to lower the film's ASA on your meter. Try cutting it in half (e.g. use 200 instead of 400).

If your shadows look good, but the high values are blocked up, then you overdeveloped the film. Try cutting your development by 20-25%. If your shadows are too dark, but the high values look right, then you underexposed and overdeveloped the film. This is very common when we use the manufacturer's ASA and develop as instructed on the film's information sheet.

Work at it; be open to adjustments. Make the process work for you. Use the same film, developer, paper and paper developer, at least until you're consistently getting the right exposures, and your prints of full-range scenes have a full range of tones.

A good negative is one that allows you to make a fine print. I would let your prints tell you what to adjust, rather than relying on a machine.