Figuring out developing times

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henryjjames
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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?

Thanks,
Henry
tim.bowman
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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.
tundratim
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Joined: Mon Dec 19, 2022 11:50 am

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:

https://gitbucket.tundraware.com/tundra/devtimer

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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