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Thread: What is EI?

  1. #1

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    What is EI?

    I recently had someone mention the EI of a camera to me. This was an older photographer. I'm still a student and was wondering what it was, I immediately thought of this sight and knew someone on here must know. It could be refering to film and not the camera. It was a very brief discussion and I shall not likely speak to him again, so I couldn't very well as him.
    Thanks to anyone who knows,
    -erin

  2. #2
    David A. Goldfarb's Avatar
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    EI refers to "exposure index," which is the speed rating of the film in combination with a developer as determined by the user, as opposed to the official ISO speed rating of the film.

    For instance, the ISO speed of 400TX (Tri-X) is ISO 400 under official standardized testing conditions, but in some developers it might only be EI 200, and in some it might be EI 640 or more.
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  3. #3

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    So do developers come with this information or is it some sort of formula you follow as you switch developers and films and what not?

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    David A. Goldfarb's Avatar
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    Most films have this kind of information on their technical data sheet (go to www.ilford.com and download some of their film sheets for some of the best examples), but even this is just a starting point, and you can do your own testing for best results.

    There are a number of approaches to film testing. I like the method that Ansel Adams describes in his book, The Negative, but you can also just start with the manufacturer's recommended speed and adjust based on your results. Adjusting the EI will change the amount of shadow detail that can be recored on film in general, and adjusting the development time will change the amount of contrast. If your shadows are always blocked up, lower the EI, and if your highlights are blown out, reduce the development time. Alternately, if your highlights are flat, increase the development time.
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  5. #5

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    Good Evening, Erin,

    1--Both film and developer manufacturers usually have data available, either packaged with their products or on a web site.
    2--For an overall view, try to obtain a good general introductory book on photography, one which is a few years old may be devoted entirely to chemical photography rather than digital.
    3--Do a search on APUG using the name of any particular film or developer; there'll probably be information available here.
    4--Post questions in the Forum about particular film or developer combinations and you'll probably get answers (opinions??) rather quickly.
    5--Do a Google search for specific films and developers. There is, for example, an entire site devoted to Kodak's HC-110 developer.
    6--Practice and experiment!

    Konical

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    roteague's Avatar
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    I agree with David. I've always thought of EI as a personal index of what to rate film speed. I know a lot of people w ho use Velvia 50 rate it at 40, so that would be ISO 50 but EI 40.

    BTW, this is not a strickly B&W rating, although I imagine that is where you will see it mostly used; you can also use it for color.
    Robert M. Teague
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    "A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; a man who works with his hands and his brain and his heart is an artist" -- Louis Nizer

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    So is it a bit like calibrating film in your camera only taking it a step further and including developing time as well?
    Also thank you for the response. We were taught a b&w course, but 6 weeks is just not enough time to learn all there is to know. I don't recall my first professor mentioning this at all, however I do now remember my second professor performing this test for us, however I guess since I didn't recall it until now I didn't pick up on it well enough (tues, night class 3hrs long seemed to last forever) He will be teaching it again so I will ask for a refresher. Thanks again.

  8. #8
    Bob F.'s Avatar
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    Quote Originally Posted by ErinHilburn
    So is it a bit like calibrating film in your camera only taking it a step further and including developing time as well?
    Also thank you for the response. We were taught a b&w course, but 6 weeks is just not enough time to learn all there is to know. I don't recall my first professor mentioning this at all, however I do now remember my second professor performing this test for us, however I guess since I didn't recall it until now I didn't pick up on it well enough (tues, night class 3hrs long seemed to last forever) He will be teaching it again so I will ask for a refresher. Thanks again.
    Ah well.. this is the old "Give someone a fish, he will eat well tonight, show him how to catch his own fish and he will eat well forever" (or at least, until the E.U. Fisheries Commission dictate a total ban on fishing in his area)...

    To translate ( ).... To understand something fully, you have to do it yourself. Watching someone else do it, or reading about it, only gives you a fraction of the story and you are certain to forget the details. After you see it done again, pick a different film and have a bash at it yourself - it's very enlightening.

    Have fun! Bob.

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    Are you sure it was the EI of the camera, rather than film? If so, it might be the lowest light level the meter can record accurately.

    David.

  10. #10

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    No I don't know which. I had not previously heard EI of anything, and I wanted to know what it could be refering too. So yes it could be either or.

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