I was asked the other day by my friend Luis GV Caso, if there was a way of doing an exposure and development test using one roll of film. I knew how I would tackle it if I was working in my own darkroom, but I realised that I had never written this down. After I had sent it to him, I thought it would be useful to post it here.
Hi Luis,you asked if there was a way to do a full test on one roll of film. There is, but I think you would need to use 35mm, as you will need to cut the film into three sections after shooting. Doing this with medium format would leave short, curly bits of film which could become loose in the tank. Firstly, you need to think about the sort of lighting that you usually shoot in, or prefer. It is no use doing this test in full summer sun if you prefer shooting on foggy autumn days. Choose the appropriate scene and light (hopefully constant, and not likely to change for the duration of the test).
With the camera on a tripod, take a meter reading the way you normally do. This might get a lot of other photographers saying: ‘oh no, you need to do an incident reading’, or: ‘You have to do a range of spot metered readings and average them out’. This test is meant to help you get the best out of your way of working, not to get tied up in other people’s methodology or obsessions. Once you have your reading, draw out a range of camera settings which will give you a sequence of exposures from 4 stops under, all the way up to 4 stops over (see the diagram below). Shoot these nine frames, then cover the lens and shoot four blank frames. Shoot the same nine exposures then another four blanks. Shoot the last nine frames and one blank then rewind the film.
In the darkroom you will need to have something light tight that you can store sections of the film in, unless you have three tanks. Cut the leader off, then cut the film into three roughly equal lengths. The blank frames should give you enough space for error. The last length needs a small cut in the end (where the last blank frame was) to identify it. Load the first length into the dev tank and store the middle and end for now. Process this for 20% less than the recommended time. Stop, fix and wash as normal. Process the middle section for your normal time. Process the final length for 20% more than your normal time. When dry, do a contact sheet (longer paper needed for 9 frames, or tape two bits together). The test exposure to determine the correct time (for all 3 strips) should be the shortest possible exposure that will produce black under the clear edge of the film. Wash and dry the final contacts and look for the ‘correct’ frame. It should be frames number 6, 18 and 30, but your results might differ slightly. Contact printing is only an indication of the area you should be working in. You will have quite different choices for printing, depending on whether you are using a condenser or diffuser enlarger. Use the indicated frames to make test prints, but be prepared to see better results in the last section if you are using a diffuser enlarger, and in the first section if you are using a condenser enlarger.