Any advantage to scanning emulsion side of slides?

Discussion in 'Photography' started by Doc, Jan 28, 2005.

  1. Doc

    Doc Guest

    When scanning slides, I wonder if there could be any advantage to scanning
    the emulsion side of the slides and then reversing the image?
     
    Doc, Jan 28, 2005
    #1
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  2. Doc

    chrlz Guest

    From my experience (which is reasonable, if not professional!) with
    film scanners up to 4000 dpi, nothing that I could spot. But it's
    possible it *could* make a small difference depending on the optics and
    light path. The difficulty will be detecting whether it really is
    different for that reason, or whether it has just focused slightly
    better/worse..

    Why not try it on your scanner and see for yourself?
     
    chrlz, Jan 29, 2005
    #2
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  3. Doc

    RSD99 Guest

    Yes ... why would you want to scan **through** the base?
     
    RSD99, Jan 29, 2005
    #3
  4. Doc

    Doc Guest

    That's why I made the inquiry. All the "here's how to scan slides" sites
    I've seen direct you to slide the non-emulsion side to give you the same
    perspective as the projected image, but after thinking about it, I wondered
    if that could degrade the image to some small degree.
     
    Doc, Jan 29, 2005
    #4
  5. Doc

    grol Guest

    Surely because they are transparencies, the light projected through them should
    be the same either side, unless the coating on one side reflects the light. ??
     
    grol, Jan 29, 2005
    #5
  6. Doc

    J. A. Mc. Guest

    Yes, it can. but ... think this way ... In the enlarger and projector the
    light source is on the coated (non-emulsion) side and the emulsion is to the
    lens' rear port. You're doing the same thing by placing the emulsion closest
    to the glass, as most scanners today have a lens system to 'read' the item
    just above the glass.

    FWIW, I keep the slide in a Wess 'Duplicator' mount to keep anything from
    touching the actual film. This is a special mount that shows the entire
    exposed area, unlike standard plastic or cardboard mounts.
     
    J. A. Mc., Jan 30, 2005
    #6
  7. Doc

    chrlz Guest

    Can you show any examples? Back when I was a very keen film-scanner
    (about 2 years back, don't do all that much now..) this question came
    up quite a few times on the filmscanner lists I was on, but no-one
    could show any convincing evidence either way. I'm genuinely
    interested..

    (sorry if double-posted..)
     
    chrlz, Jan 30, 2005
    #7
  8. Doc

    Graham Smith Guest

    My hunch and aging knowledge of physics tell me that it would make no
    discernable difference whatsoever. I've got a micrometer somewhere and
    could measure the thickness of a transparency, but there's no point,
    quite frankly. The depth of field of your typical scanner is >> the
    thickness of the film.
     
    Graham Smith, Jan 30, 2005
    #8
  9. Doc

    RSD99 Guest

    It's not about "depth of field" ... it's about putting the crap,
    aberrations, dirt, and distortion of the *film base* between the scanner
    and the image.

    It was never designed to be used that way. The film base is simply a
    substrate to support the emulsion, and is/was never "controlled" as part of
    the optical chain.
     
    RSD99, Jan 31, 2005
    #9
  10. Doc

    chrlz Guest

    Yep, and there's also the issue of the light path and optics - the
    light paths in flatbed/film/drum scanners can be quite different to
    that of a projector (and of the taking lens for that matter). Just
    like in enlargers, some clearly use more/less parallel/diffuse light
    sources than others, some *do* have extremely limited depth of field
    (eg nikon LED scanners). So to dismiss the idea that turning the film
    around will have no visible effect may be a bit rash.

    To start another argument ((O;) it's a bit like saying that an
    optically flat UV filter will have no effect on the sharpness of your
    images. In fact, if you start looking at it very closely and looking
    at the light path and how it is affected by that (admittedly small, but
    *extra* refraction), you will see it may not be quite true..

    But to contradict myself (grin) - like I said above, I have not
    actually seen direct evidence of a difference, and it would be pretty
    hard to prove that it wasn't just a slight difference in focus.
     
    chrlz, Jan 31, 2005
    #10
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