What does unexposed reversal film look like?

Discussion in 'Photography' started by Curious George, Apr 11, 2006.

  1. Somehow I always had it in my head that it was opaque to start with and
    then turned more or less transparent after exposure and development. It
    occurs to me that this is probably wrong and it probably starts off
    clear and just turns dark the opposite way that negative film does,
    i.e., the highly exposed parts don't change and the unexposed parts get
    dark when developed. Can somebody tell me or do I have to waste a roll
    of film to find out?
     
    Curious George, Apr 11, 2006
    #1
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  2.  
    Curious George, Apr 11, 2006
    #2
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  3. Curious George

    Whiskers Guest

    If you can find a way of seeing a film without exposing it to light, I
    think we'll all be interested ;))

    Undeveloped film is always pretty opaque, not least because of the need to
    ensure that no light can get to the back of the emulsion and be reflected
    through the emulsion again.
     
    Whiskers, Apr 11, 2006
    #3
  4. Curious George

    m Ransley Guest

    It starts out dark like film
     
    m Ransley, Apr 11, 2006
    #4
  5. He didn't suggest otherwise, or ask about it either.

    But it is a little silly to waste a roll of film... given that
    virtually every roll has a leader of undeveloped film which can
    easily be inspected, for example while loading it into a
    camera...
     
    Floyd L. Davidson, Apr 11, 2006
    #5
  6. Curious George

    Whiskers Guest

    <pedantic mode on>

    Actually, he did - in the subject line; he then re-posted a bit later with
    a better subject line, to be fair, but I couldn't resist <G>
     
    Whiskers, Apr 11, 2006
    #6
  7. Hmm. It has been many years since I developed film and I never
    developed reversal film, but it seems to me that, in that dim darkroom
    light, the film was clear until I put it in the developer. I don't
    think I should have seen the film if I was doing it right, but it seems
    like I did. Maybe I was just curious.
     
    Curious George, Apr 11, 2006
    #7
  8. Curious George

    Pat Guest

    All "film" is nearly clear but has a dark, nearly opaque emulsion
    layered on it. So what you see before anything happens to it is dark.

    On "negative" film (which may be what you are calling reversal film),
    the light strikes the emulsion. The more light, the darker it get.
    When you put in through an enlarger, the same thing happens: the more
    light the darker. So if a lot of light strikes the negative, it
    creates black. That black blocks the light from reaching the paper and
    makes white. Got it?

    If you process an unexposed roll of film, you get nothing. That would,
    in theory, print as black if you were to do that. Here's your proof
    (without killing a perfectly innocent roll of film). Look at a
    negative. All around it is clear space (not black space). I mean the
    area near around the sprocket holes that has the writing and between
    the individual images. That is totally unexposed film that has been
    processed.

    I haven't shot slide film in decades, but I believe unexposed film is
    black after processing. So it starts black, if you will, and gets
    lighter with exposure. This is why movie film -- that you see
    everywhere -- is totally black except where the positive image is.
    That's why it's used for the opening of films, etc. If it was clear it
    would look weird.

    Hope that clarifies things (and I hope I have everything right).
     
    Pat, Apr 12, 2006
    #8
  9. Curious George

    Whiskers Guest

    snip
    Looks right to me (for what that's worth).
     
    Whiskers, Apr 12, 2006
    #9
  10. Curious George

    m Ransley Guest

    I pulled out an expired roll of K 25 it wasnt clear I remember that, but
    I forget how dark it was.
     
    m Ransley, Apr 13, 2006
    #10
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