Figuring out developing times

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Figuring out developing times

Post by henryjjames »

Hello all,

I am seeking advice on how to calculate development times when the film/chemistry manufacturers do not provide the data, nor is it available on the massive dev chart. Does anyone have suggestions or methods on how to calculate a development time for a film other than pure trial and error?

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Re: Figuring out developing times

Post by tim.bowman »

Lots of folks like the Massive Dev Chart for this. But I actually prefer trial and error. Take your best guess, make a print, and see how it goes. If you're struggling with shadows, give the film more exposure next time. If it's too contrasty, develop less. If it's too flat, develop for longer.
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Re: Figuring out developing times

Post by tundratim »

I built a temperature controlled darkroom timer some years ago and faced this problem. You'll find a spreadsheet on the git repo that calculates these factors a number of different ways:

I used a couple of theoretical mathematical models as well as actual published data from Kodak (and maybe Ilford, I don't recall), and then compared how much they varied from each other.

The actual program has two lookup tables - One for film and one for paper - with correction factors for temps in one degree F increments away from a nominal 68F. These correction factors were the results of the analysis above.
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