Testing Film Speed

[Jean Nightingale]

I've just got new spot meter and I want to try and get my film speed sorted out. The instruction to photograph plain card in even light I find harder said than done! The card can meter a 1/3rd of a stop difference over its area.If the light outside changes you're in difficulty again trying to take 4 or 5 shots. Is the only way to do it, is with a longer lens and close up to card, so that only a small portion is being photographed. I wasted some film last time I tried this.
Jean

[Andrew O'Neill]

It's best to do all your film testing under the same lighting conditions. For consistency, I decided to do my testing inside. I bought a couple 500W daylight balanced light bulbs from local camera shop. These were placed inside a reflector and positioned so that target was evenly lit. My target was a middle gray wall in my darkroom.
Remember if you focus in close you have to compensate for bellows extension. With a setup like this where all the variables don't change, you will have best results.
I did it this way until I discovered the zone board in Hutching's book about Pyro. Much better.

[Ron Marshall]

I test inside with incandescent light as well. One less variable to be concerned with. I make sure I have enough light to avoid having to make a reciprocity correction.

[Brian Ellis]

When I did my own testing I tested outside since that's where I'll be photographing and I remember Fred Picker talking in his book about some adjustments that need to be made to the results when testing under artificial light (probably unimportant but I didn't want to worry about it). While lighting conditions outside can change, when you expose film for a film speed test all you're doing is making about five exposures at different f stops. Nothing else changes. You can make five exposures in a minute or two if you move fast. Surely you can find some open shade on a cloudless day where the light won't change in that short a period of time. Better yet, spring for $35, let The View Camera Store do your film speed (and development time) testing for you. I can almost guarantee that by the time you finish with both EI and development time tests using traditional zone system testing methods you'll have spent close to $35 in film costs alone. In addition, The View Camera Store will provide you with more and better information than you're likely to get on your own.

[Bruce Barlow]

Once you've exposed it, what do you do with it?

www.circleofthesunproductions.com may offer help.

It's Picker's method, updated, and endlessly repeatable if you love testing.