I undertook the endeavour of film testing a few months ago when I was only shooting 35mm, because I seemed to be underexposing everything using the film (FP4+) box speed and Ilford's development time for Ilfosol S (6 1/2 min). On the 35 mm frame, I came up with a film speed of ISO 64, but didn't get around to testing development time, as I aquired a view camera.
So, I've tried doing some 5x7 film (FP4+) testing using an "inspection" approach, as I have no densitometer. Essentially placing a dark cloth on zone 1, making 5 exposures and developing by manufacturer's recommendations (Ilfosol S for 6 1/2 min). Then using a 0.1 ND filter on a piece of developed unexposed film, comparing the 5 pieces to determine film speed. Here lies problem #1. For the life of me, I can't get a piece of film with equal density across it, so my comparisons are invalid. I don't think it's my developing technique, as I've developed a number of actual photos I've taken, and none are uneven. I actually have found tray processing of the film quite easy from the start.
To find development time, I made 6 exposures of a white wall placed on zone 8 using the "film speed" I determined in step one (I used the closest piece of film I could find in what I was already considering a flawed test- ISO 64). I developed the film and started removing pieces to the stop bath every 30 sec starting at 5 1/2 min. Next is a contact sheet made with half of each piece of film covered for the minimum time to achieve maximum black on the paper. Once dried, I am to inspect each interface on the paper where the film was covered looking for the faintest hint of tone, thus being Zone 8, and that piece of film was developed for the correct time. Here lies problem #2. For the life of me, I can't reliably see a faint trace of tone for *any* of these pieces of film. I can maybe convince myself that I saw a trace on 2 of the samples, so that would indicate a development time of 6 min at 20 deg C.
I tried some still life's of some flowers, and when I contact printed them, they were way overexposed, overdeveloped or both. I was also reading BTZS at this time, and was considering having the testing done for me. Before doing that though, I wanted to give it another try using HC-110 at 1:31. I had not been happy with Ilfosol's shelf-life. So, I did it again, had the exact same problems, came up with a film speed of ISO 80 (which I don't trust) and a development time of 6 1/2 min (which I also don't trust).
I'm pretty fed up with this scheme- I am obviously inept at something, because in all these books I've read, the authors make it sound so simple to set up a card and make the exposures, etc. This is very frustrating to me, because it all seems so simple, makes perfect sense to me in theory, and I work in a very methodical fashion. But my results are crap! I'm throwing the Zone System out the window once and for all, along with doing my own testing. I'll let the View Camera store do the testing for me. BTZS makes more sense to me anyway.
Just out of curiosity, what are other people rating FP4+ at and how long are you developing for in HC-110/ Ilfotec HC, and in Ilfosol S?