Exposure Latitude

Discussion in 'Film and Processing' started by christian_canturia, Feb 2, 2016.

  1. So can someone explain this to me? I'm a little confused by it. Also, when I'm shooting film, can I have a different iso than the one set on the box without having to process the film longer or vice versa? for example shooting 100iso film at 400iso, will I have to develop the film longer or will it be okay to have it developed at 100iso still?
  2. Exposure latitude is basically how forgiving the film is of over/under exposing it. For instance, if you were to shoot Kodak TriX 400, you could underexpose it by 5 stops [shooting above ISO 1600 is probably suicide anyways] or underexpose it by 2 [down to ISO 100] and still get relatively good results.
    If you want to develop it as ISO 400, you'll probably be fine even if you over/under exposed it within those limits. Alternatively, you could push/pull process the film. If you think you've overexposed every shot, you can specify pull processing to 'pull' the film ISO back by however many stops you want. So if you want to pull two stops you'd get an ISO 100 result from it [It'd go ISO 400->200->100]. The same goes for if you underexposed it, you can use push processing to 'push' the film ISO to whatever you desire.
    It's important to know the exposure latitudes of your film so you don't under or over expose the film to the point where it's difficult/impossible to recover
    Hope this helps a bit
  3. Film needs a certain amount of light to work. Sensitivity is designed in and can't be changed.
    A film rated at iso 100 needs a lot more light than one of iso 400. (four times as much as it turns out).
    If you underexpose the film, it doesn't get enough light, and even though you might get a picture it won't be as good as it should be.
    That's why they invented light meters and there are millions of words written about how to expose film.
    But in the end, it is Film and it needs Light.
  4. Les -- I really like that effort using the Toyota truck. You demonstrate a good mastery of scanning technique as well. Can I ask what scanner and software you use?
  5. Technically, ISO is a property of the film, and you can't change it.
    You can expose film AS IF it had a different ISO value, in which case it is commonly called an EI (exposure index) value.
    With simple, non-adjustable, cameras, exposure latitude is what allows you to use the camera in different lighting situations. For adjustable cameras, it allows for metering of the wrong spot, or other errors in deciding on the exposure.
    Films are normally designed for 10 zones, that is, for the lighter parts to be about 1024 times brighter than the darker parts. Latitude is how much more than that, the film can handle.
  6. The fun of film is the quirks it has. I have over and under exposed film and had it processed normally. No harm done.
  7. If you want to shoot at 400, use film that has an ISO of 400. You'll get better, more consistent results.
  8. I like consistent results and I feel good about knowing what I have in the box after exposure. Anyway these days I am pretty much shooting 400 speed B/W film at 400. Tri-X currently is on the menu for 10 rolls.

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