View Full Version : Film Testing

7-Feb-2007, 14:20
I am in the process of trying to do some film tests according to the Zone System in 35mm so I can apply it to my LF endeavor (starting cheap). I think understand the concept - Find the correct film speed that gives you detail in Zone 3, then find the development time that gives you good detail in Zone 8. Then it all got turned on its ear when I was reading a thread at P.net and someone mentioned Barry Thornton's "Edge Of Darkness". He sais that for depending on the brightness of the scene, rate the film at box ISO (cloudy, no shadows) and develop as recommended, and to rate the film at 1/2 box iso and decrease development by something like 20-30% (bright sun, sharp shadows). I thought that film testing was to give you the film's speed, regardless of the light outside! Is his vernacular just another way of deciding on exposure and N minus development for scenes that have a long exposure gradient for "non-zonies"? I'm trying to wrap my head around his use of box ISO for cloudy scenes and normal development though. It seems that film is always slower than its box ISO.....

Thanks again,

Ed Richards
7-Feb-2007, 14:48
1) Find a good book

2) Remember that for many films, the 35mm version is a different emulsion from the 4x5 version.

7-Feb-2007, 15:11
There are dozens of ways to test for film speed and development times. Here is one of the simpler methods:

My guess is that testing with 35mm and trying to apply the data to LF would be a worthless effort.

Bruce Watson
7-Feb-2007, 15:25
I thought that film testing was to give you the film's speed, regardless of the light outside!

Close, but not quite. The purpose is to find your personal exposure index (EI). Your EI may or may not differ from the film's ISO rating. It depends on many things, including the developer you choose, the dilution you choose for this developer, the way you choose to process (from continuous agitation to full stand), your personal shutters, your personal lightmeter.... you get the idea. It's about calibrating your entire system.

And yes, once you find your personal EI you use it for all your calculations. You may find that you increase your exposure a bit when you decrease your development time for example, but that increase will be based on your EI, not the ISO on the box.

All that said, "there are many paths to the waterfall." That is, there are lots of ways to do what you need: expose and process the film to capture the detail that you want captured. Find a method with which you are comfortable, learn it well, then go about making some photographs.

Erich Hoeber
7-Feb-2007, 18:28
Steve Simmons article is a great place to start.


For an exhaustive - and excellent - treatment, see the book Beyond the Zone System by Phil Davis.

35mm is unlikely to help you, and not JUST because the emulsion can be different from the sheet film version. The method of development will invariably be at least somewhat different as well, and this could also skew your results.


7-Feb-2007, 19:57
Get a copy of the Simplified Zone System. Nice and to the point.