Pushing film, and EI

Discussion in 'Film Discussion and Q & A' started by frXnz kafka, Oct 22, 2007.

  1. frXnz kafka

    frXnz kafka TPF Noob!

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    I've got a couple questions regarding film speed. I'm mostly concerned with black and white film, but I'm sure some of this applies to color film as well.

    First, what is the difference between ISO and EI?

    Second, let's say I'm using a 400 speed film, and I want to push it to 1600. What changes? I assume I'd change the ISO setting on my camera to 1600, but what changes in the development process? Is there a general rule of thumb for figuring out developing times, or is it more or less guess and check?
     
  2. ann

    ann No longer a newbie, moving up!

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    EI stands for exposure index which is discovered by film testing, which is not guessing, but serious testing of film and development combination.

    ISO is the speed that the manufactor has determined.

    Pushing the film is going from 400 to 1600, and what really occurs is an increase in contrast with increased development times which is a by product of pushing the film.

    You will need to increase the development times as you increase the ISO .

    Rule of thumb is about 20=25% per each fstop of push.
    What your really doing is allowing more options with your fstop or shutter speeds, which will allow you to get some image in very low light conditions. However, you must also increase the development times.
     
  3. frXnz kafka

    frXnz kafka TPF Noob!

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    So if I'm pushing 400 speed film to 1600, I should develop for about 40-50% longer?
     
  4. Helen B

    Helen B TPF Noob!

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    In addition to using ann's rule of thumb, you could look in the Massive Dev Chart or manufacturer's tables such as this pdf from Ilford.

    Which film and developer combination are you using?

    Best,
    Helen
     
  5. frXnz kafka

    frXnz kafka TPF Noob!

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    I'm using T-Max developer, and I'll probably try this with some Ilford HP5 film.
     
  6. Helen B

    Helen B TPF Noob!

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  7. frXnz kafka

    frXnz kafka TPF Noob!

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    I think I have a roll of Tri-X (or maybe it's T-Max) film kicking around. Have you had any experience with that?

    Thanks for the datasheet.
     
  8. frXnz kafka

    frXnz kafka TPF Noob!

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    Well I developed a roll of Ilford HP5+ that I pushed to 1600 today. I haven't enlarged anything yet, but the contact sheet looks great. I think I might try to push a roll of 400TMax to 3200 next :D
     

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pushing color film