Interesting Leica product announcements today ...

Discussion in 'Digital Photography' started by Bruce, May 10, 2012.

  1. I do not agree; most especially with a basic color filter, which does
    nothing more than blocking some amounts of some colors of light -- a
    classic case of "removing information" if there ever was one.
     
    David Dyer-Bennet, May 15, 2012
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  2. True, but not a particular problem with actual digital cameras as used
    in the field for actual shooting, including sports (heavy shooting).
    Room temperature to slightly higher, and based on RAW files (that's a
    deliberate evasion; I do not know for a fact whether or not my cameras
    do some noise-removal processing before writing what they call RAW
    files, so I can't answer your actual question).
     
    David Dyer-Bennet, May 15, 2012
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  3. Yes, of course it is, and that doesn't change anything. Removing some
    light can make two things that looked "different" originally look "the
    same".
     
    David Dyer-Bennet, May 15, 2012
  4. But we're talking about physical possibility, not
    mathematical. Mathematical impossibility only implies physical
    impossibility when all the assumptions made in converting the
    precursor conditions into mathematics hold. The history of science and
    technology has plenty of examples of things that had been proved
    mathematically impossible right up to the point when someone ignorant
    of the proof did it.
     
    Chris Malcolm, May 16, 2012
  5. Ok, let's suppose for the sake of argument that I'm missing 90% of the
    light. So I increase exposure by 10. No problem.
     
    Chris Malcolm, May 16, 2012
  6. I was simplifying to get the point across. What you're describing is
    moire effects. That's one kind of aliasing artefact, and it does
    happen because a near-pixel size transition is moving across pixel
    boundaries. With regular repetition you get moire patterns, but that's
    not the only kind of aliasing artefact.
    It's not just patterns. Patterns produce the very obvious moire
    artefacts, but they're not the only aliasing artefacts, just the most
    glaringly obvious.
    What matters is what the camera does, not what the photographer is
    trying to do. Shadow or high ISO detail which is very noisy and to
    which no noise reduction has been applied strongly resembles a
    pointilist painting. And anyone who has played with sophisticated
    adjustable noise reducers trying to remove as much noise as possible
    without losting detail from a very noisy image has noticed that
    there's a definite compromise between noise reduction and detail
    resolution. If you want to see all the perceptible detail you have to
    leave quite a bit of noise in the image. If you want a clean noise
    free image you have to lose some detail.

    The same goes for anti-alias filtering. I'm not talking about aliasing
    artefacts being mistaken for detail. I'm talking about real detail
    which can be verified by examining the objects photographed.
     
    Chris Malcolm, May 16, 2012
  7. I think most DSLRs have menu-switchable long exposure noise
    reduction. When activated and if you take a long exposure it takes a
    second exposure of the same length with shutter closed, a dark
    exposure, and subtracts that from the original shot. It affects the
    RAW file if shooting RAW.
     
    Chris Malcolm, May 16, 2012
  8. I know *that particular one* is switched off in mine. I haven't heard
    that mine does other pre-RAW processing. But, since the code is
    proprietary and I haven't heard about serious work with disassembly, I
    don't feel I actually *know* it doesn't do anything else.
     
    David Dyer-Bennet, May 16, 2012
  9. I trained as a theoretical mathematician, while working (and I have
    continued to work ever since college) as a software engineer. I feel
    like I know something about theory, and a little bit about the real
    world.

    They're not the same. People claimed for years that it was
    mathematically impossible for bumblebees to fly. The math was right,
    too; problem was, they were using it improperly (modeling bublebees as
    fixed-wing aircraft!). That kind of thing happens a lot -- people apply
    correct mass to an incorrect model, and get nonsense results out.
     
    David Dyer-Bennet, May 16, 2012
  10. You can see grain quite clearly with moderate optical magnification; a
    few tens.
    In a compressed format, including LZW-compressed TIFF, a noiser image
    will compress less well, and I *think* he may have been alluding to
    that.
    The stuff we saw in 11x14 optical prints from TRI-X is what was called
    "grain". That's an optical magnification of just over 10x.

    You're going to insist those are "grain clumps", right? I think I know
    this trick. They're universally referred to as "grain" by people
    describing the appearance of optical darkroom prints.
     
    David Dyer-Bennet, May 16, 2012
  11. I'm kind of leary of simplistic mental models masquerading as
    mathematical certainties, myself.
    Probably a German; unfortunately, the link Straight Dope gives is no
    longer working.

    Can't be magically and automatically recovered, no.
     
    David Dyer-Bennet, May 16, 2012
  12. Nonsense.

    The identity filter discards no information from any source.

    Many other filters discard no information from *particular* images.

    (Since you seem to like playing the extremist literalist!)
     
    David Dyer-Bennet, May 16, 2012
  13. In fact, the removal of the information is fundamental to that image.

    As we have already established, not everybody agrees on what "useful"
    uses of color-rendering filters are, so blanket statements about why
    people use them are probably untrue. Furthermore, people doing
    something other than art photography may make VERY different choices --
    forensic and scientific photography for example.
     
    David Dyer-Bennet, May 16, 2012
  14. Mostly, it *improves* image quality.
     
    David Dyer-Bennet, May 16, 2012
  15. Bruce

    Trevor Guest

    All very true, but what most people call grain in any B&W negative, is in
    fact grain clumps, which are readily visible with HQ scans and enlarging
    lenses.
    MY grain focuser still worked for me, and many other people I know, with
    Tech Pan under the enlarger. And I had much more experience with Tri-X and
    dozens of developing solutions, which all produced readily visible grain
    clumps, regardless of the visibility of "individual" grains.

    Trevor.
     
    Trevor, May 16, 2012
  16. Bruce

    Trevor Guest

    If you know you are going to only use one channel, and you do if you would
    otherwise use a filter, then simply allowing the unused channels to clip is
    not an issue for any modern camera with seperate histogram per channel
    display.

    Trevor.
     
    Trevor, May 16, 2012
  17. Photon-limited noise arises purely because of the /number/ of photons, and
    the statistical nature of that. Thermal noise is over and above that.

    Cheers,
    David
     
    David J Taylor, May 16, 2012
  18. Bruce

    Trevor Guest

    True for recent DSLR's of course, but not a universal truth as quoted. I
    guess you just haven't "tried" those that are not :)

    Trevor.
     
    Trevor, May 16, 2012
  19. Bruce

    Trevor Guest

    As I pointed out in another post, that relies on grain clumps, which most
    people call grain because it is the normal state for B&W negatives. The
    mathematical argument relies on individual grains *theoretically* not
    clumped. Sort of like saying you can't see the individual atoms in a grain
    of sand without an electron microscope. You can easily see the grain of sand
    however.

    Still have all those including all my darkroom equipment in the next room,
    and I know exactly where. :)

    Trevor.
     
    Trevor, May 16, 2012
  20. True back to my first DSLR in 2002.
     
    David Dyer-Bennet, May 16, 2012
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