zone system/film processinggreenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
I just developed my first 120roll of Delta 400 in Xtol. The negatives look very nice to me but I was wondering how I determine if the 10.5 minutes I gave the file shouldn't be increased to 11 minutes or decreased to 10 minutes. In the Zone VI book I have it suggests exposing a roll to zone on at asa, 75% asa, 50%asa and 25%asa and then checking with a densitometer. Is there agreement that this is a good approach to finding the best time/asa for a given film or does someone out there have another suggestion? I would have thought that I should also expose for zone V and X to test those out as well. P.S. thanks to the folks who helped me out a month or so ago with the problem I was having with my Xtol. It DID turn out to be a bad batch from Kodak and they replaced it. Regards, Anthony
-- anthony (firstname.lastname@example.org), February 23, 2001
This might be a more general answer than what you asked for, but the Zone System essentialy stands between a pure sensitometric approach, perhaps exemplified by Phil Davis' Beyond the Zone System, and an approach which just relies on experience and knowledge of one's materials. If you want all of the data, then you'd better get a densitometer and plot curves for your film, but also for your paper, because doing one without the other doesn't make sense.
Personally, I do not feel the need to do this. Studying the Zone System has been very helpful in getting me to understand how the film works, but I now take a very simplified approach. It consists of ONLY finding the ISO fo any given film and developer combination by shooting a few frames on Zone I and then printing them, using my standard paper, paper developer, and filter setting.
First, I shoot 3 or 4 frames at around the ISO which I think the film will be and develop it at a standard time which the manufacturer, or others have recomended. Then I find the shortest printing exposure that will yield maximum black for a blank frame (fb+f), and use that enlarger exposure to find the first frame Zone I frame that will give me a hint lighter than maximum black. This is my ISO for that development time. It takes into consideration my film, paper, developer, etc. I don't worry about finding Z 5 or 8 or whatever. This just comes with experience. I know what a contrasty neg. and what a flat neg. and what a normal neg. is when I print it. I intuitively find the times for pulling the film or pushing it approximately 1 zone or two zones. Even if you determine sensitometrically what an N+1 development is for example, nothing guarantees that your eye will know exactly that this or that part of a picture should be pushed from exactly zone 7 to zone 8, and not zone 8.25. Plus, your meter, shutter speed, thermometer, will all have small margins of eror.
The advantage with my approach is that with a new film-developer combination, I can go out and shoot some shots on the film, leaving only 3 or so frames for exposing a gray card (or in my case a calibration device which you can find on circada.com) at Zone I. For example, in the case of Delta 400 in XTOL, I might guess that the ISO will be either 250, 320 or 400, so I just expose for Zone one for these three settings. With 3 frames, I have a starting point, and when I print the negs, I can judge if this particular time resembles my normal, or maybe a normal minus one-half, or whatever. The next film I shoot, I might develop at a corrected time, and if this time is significantly different, retest the ISO using three frames of that film.
To me, this is the minimum testing necessary, and allows me the most time to just shoot and have fun, and it allows me to try out new film developer combinations without doing extensive testing. But each one has their own way. Good luck.
-- Raja A. Adal (email@example.com), February 24, 2001.
I recommend rating the film at half the published rating, for starters (e.g. HP5 (published iso: 400), rate at 200). Determining correct development time can be done this way:
Point two light bulbs at a white wall -- some texture preferable -- (45 degrees to about refections), and shoot the wall, placing it in a zone VII.
If using roll film, cut the film into three sections. Develop one section at your projected "n" developemnt time.
Then print this negative test strip style (2 1/2 grade filter), with two second intervals, being sure to print some of the clear film base, along with the zone VII (wall) image area. The interval at which the clear film base turns black indicates the minimum print time. What does the zone VII wall look like here? If it prints a zone VII, then you have the correct development time. If its a zone VI, you've underdeveloped, if VIII, over developed.
If its off, repeat with the other pieces of film. If you got a zone VIII, reduce developemnt by 20% (generally 20% per zone), or increase, if its a zone VI. This will then be your corrected "N" Be sure to keep dilutions, agitations and temps constant.
For film speed, photograph a well textured, uniformly lit subject, and place this in zone III. Develop the film at your newly determined N development time. Once again, determine the minimum print time (as above). If, at the exposure where your film base goes black, you get a nice zone III (good texture, but almost black), then you've got the correct film speed. If the image area is a zone II or less, then you need to rate the film lower (maybe one stop ~ 100 ISO for my HP5 example). If you get a zone IV (the "blacks" are muddy), rate the film one zone higher 300 ISO for my HP5 example).
Good luck and have fun!
-- Chris (Gazebo50@hotmail.com), February 27, 2001.