Question About EI

Discussion in 'Exposure Discussion' started by Squirt, Feb 28, 2013.

  1. Squirt

    Squirt Member

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    Hi, I am brand new to APUG and to large format photography. In fact, my Pacemaker Speed Graphic just arrived yesterday. There are some terms I am unfamiliar with and I was hoping someone on this forum could help. There was a gorgeous photo on Flickr I really liked (http://www.flickr.com/photos/ulvo/4291950562/) In the description it said:

    Fomapan 100 @ EI 50 (over-exposed by one stop)

    I know the film, but I'm unsure if EI means exposure index??? And how does one get EI 50 on a Speed Graphic? This isn't Aperture or Shutter speed, is it? I'm so sorry, but I really don't get what they mean and I've been seeing EI a lot!! I'd really appreciate it if anyone who would be kind enough to shed some light on what this really means and what they're doing. Even enough so I can continue my research......thanks!
     
  2. Roger Cole

    Roger Cole Member

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    You have it right. EI means "exposure index." Technically, any time you expose at other than the speed specified as ISO, you are not exposing at ISO. There is only one ISO because that's a standardized speed with strictly defined criteria. Anything else is an exposure index.

    It refers to the film speed. You "get" EI 50 with any camera the same way - you take a meter reading, either with an internal meter or, in the case of a Speed Graphic with an external one, and set the film speed to that speed, or adjust from a different setting to get that effective setting. With a manual camera you transfer the shutter speed and aperture for that exposure to the camera lens and shutter.
     
  3. polyglot

    polyglot Member

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    Yes, EI is Exposure Index. It's a description of how much you exposed the film (bigger numbers are less exposure), so it is a function of the meter reading, the aperture and the shutter speed.

    Simplest way to achieve a specific EI is to set your meter's ISO setting to that EI, take a light reading and put those settings (aperture and shutter) onto the camera.

    ISO is a definition of how much exposure a film should get for normal exposure and development, EI is how much exposure you actually give it. Most people find that Fomapan is quite optimistic in its ISO rating, i.e. they get less shadow detail than they want, so they expose it at EI50 instead of EI100. 50 is twice as much exposure, i.e. one stop more, which gives more shadow detail and a denser negative.

    Usually when adjusting EI, one would also adjust development. You don't just randomly pick an EI, you typically decide on how much contrast you need for a particular scene, which defines how much development you're going to give that sheet, which defines the appropriate EI. Have a read about Zone System and Beyond The Zone System (BTZS).
     
  4. Poisson Du Jour

    Poisson Du Jour Member

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    EI = exposure index, an abritrary "re-rating" of the film to suit the contrast values of a scene or your prior experience (ideally) with that particular type of scene's contrast.

    Typically EI references a different film speed to provide over-or under-exposure. An example is Velvia (transparency film with a bad temper! :smile:) rated at EI40 is +0.3 (third-stop) over-exposure; EI32 is +0.6 (often too much!). It's never referred to as ISO40 or ISO32. Negative films have a lot more exposure than slide films, and so an EI is often given in the range of one or two stops above or below, then development adjusted to suit. EI has more use in LF where sheet film allows individual development to a very fine degree. With roll film (120, 35mm) you are simply giving more or less exposure to suit and possibly even then specifying push or pull processing (something else for you to learn ... later!)

    The best way to learn about exposure index is to load some film up, re-rate it (e.g ISO 100 film to EI 200, maybe other indices), expose it normally but importantly, keep notes as you go along so you can reference them examining the negs/trannies.
     
  5. Sirius Glass

    Sirius Glass Subscriber

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    Welcome to APUG
    Additional Pacemaker Speed Graphic information is available at www.graflex.org

    I use the film box speed with all my cameras including a 4"x5" Pacemaker Speed Graphic and 4"x5" Graflex Model D. The latitude of black & white and color print film is so great that if your light meter and shutters are reasonably accurate, and good light metering techniques are used, the box speed works quite well. I have never found that film testing showed enough deviation to make any change necessary.
     
  6. AgX

    AgX Member

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    EI = speed setting in analogy to ISO, BUT based on your specific process, requirements and expectations
     
  7. Gerald C Koch

    Gerald C Koch Member

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    Very simply ISO is the film speed that the manufacturer determines for a film. EI is the speed which produces the best results for your camera and processing method.
     
  8. MattKing

    MattKing Subscriber

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    In Canada, it means "Employment Insurance" :smile:.

    As others have posted, it means Exposure Index when you are talking about film photography.

    It is the light sensitivity rating for the film you use with your meter. Sometimes referred to as the "speed" of the film.

    It reflects your practice, your exposure preferences and your equipment. It is usually close to or identical to the standard ISO ("box") light sensitivity rating for the film, but not always.
     
  9. michael_r

    michael_r Subscriber

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    :laugh:
     
  10. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Welcome to APUG, Squirt! You have asked an important question, and you got good answers here. If you stick with this sort of photography for a while, you will have many more questions about EI, ISO, development times, CI, gradients, and much much more. It may help you to get along this wonderful journey to read up something that will explain it all in a gentle, concise and authoritative way. One of the best such reads is a set of three books by Ansel Adams, titled: The Camera, The Negative, and The Print. Get the more recent editions.

    Enjoy, and keep asking questions.
     
  11. Squirt

    Squirt Member

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    Awww, a BIG thank you to everyone! It's nice to know there are people that care enough to help. Everything I learned, I learned by myself...scrounging around on the internet. I've been dying to work with large format and thought it really couldn't be that different than 35 mm or a medium format camera with a meter. Boy, I was wrong!! I wasn't getting EI, because first of all, I didn't realize that I should have a light meter!! (DUH). I went through the entire Speed Graphic Manual but I realized yesterday morning, I didn't know how to change the film's ISO on the camera, LOL, until I thought about it a bit. Now the whole EI thing is starting to make sense. Initially, I was figuring I would just take my digital along and use that (and I guess I could, but don't think it would work quite as good as a light meter which I purchased today from B&H). Thank you again for answering all my questions. You folks are wonderful!
     
  12. Squirt

    Squirt Member

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    Thanks Rafal! I just picked up all three at a used book store about two weeks ago (I had read about these books and I have been thumbing through them, and there's a lot of info in there.....).
     
  13. Roger Cole

    Roger Cole Member

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    You CAN take your digital along and use it, but it may take some tinkering to figure out the best translation. The meters are, naturally enough, optimized for their digital sensors, and they may also make decisions based on metering matrices that may, or may not, work with what you want to do. Ideally I'd recommend a manual camera and hand held meter. But if the meter is another item you don't want to purchase yet and you have a smart phone there are metering programs available. I have an ap called "Pocket Light Meter" for my iPhone that is pretty versatile and agrees closely with my other meters. IIRC it was free (ad supported) though you can pay the developer just $0.99 to get rid of the ads. I've been meaning to pay the $4.99 to get rid of the ads and, as he says in the settings, "buy the developer a pint!"
     
  14. Poisson Du Jour

    Poisson Du Jour Member

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    You could take your digital camera along with you but set its meter to centre-weighted average. The high-tech matrix/evaluative/multipattern meters are calibrated along the Zone System with additional metrics overlaying this to assist with "judgement" by the camera (that is, after all, looking through a library of many thousands and thousands of images just like the scene you are viewing).

    Otherwise, invest in a high quality meter that you can build your skills around. I don't regard using a digital camera to build knowledge the way to go: it has scant resemblance to the characteristic of film. This is especially true for MF and LF. At a later date, getting the hang of spot metering (something an iPhone does not have -- still!) for very precise analysis of scenes would go a long way toward rewarding you with beautiful, luminous images from MF/LF.
     
  15. Bill Burk

    Bill Burk Subscriber

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    Hi Squirt!

    Welcome to APUG.

    I've just come to realize that EI is meant to correlate your light meter to a study "Picture Tests".

    A group of people were told to pick their favorite prints out of a pile.

    The idea was to come up with a number to set on the meter that will make most of your prints end up in the "good" stack.
     
  16. Maris

    Maris Member

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    That's like how I work when I have to use a new film or developer and I'm in a hurry. There is a "standard" front lit scene every mid-morning near where I live. Direct sunlight is very consistent all year round because I'm near the Tropic of Capricorn.

    I expose 4 sheets of 4x5 film in my camera with a stepped exposure sequence across each one done by pushing in the darkslide a little bit between clicks. I go from two stops under to two stops over in five steps. Because my darkroom is closeby I immediately develop all four sheets at different developing times. Within an hour I know the correct exposure for the scene. All I have to do is set a number on my light meter so that my usual metering strategy delivers the exposure reading I already know is correct. That's my film EI. And this test procedure also gives me the right development time either directly or by interpolation.

    Certainly this is not a laboratory standard test but it is quick and the directness of it inspires confidence.