Any Minolta/Sony users using UFRaw and GIMP?

Discussion in 'Digital Photography' started by Jeffery Small, Apr 5, 2014.

  1. Jeffery Small

    PeterN Guest

    Another really logical statement, without factual basis.
     
    PeterN, Apr 20, 2014
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  2. Jeffery Small

    PeterN Guest

    You've said that before, and rceived a logical answer.
    do keep up
     
    PeterN, Apr 20, 2014
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  3. Jeffery Small

    PeterN Guest

    the title of this thread is.......
     
    PeterN, Apr 20, 2014
  4. Jeffery Small

    PeterN Guest


    The only time you might see a difference would be if there were colors
    in the LAB spectrum that are not in the RGB spectrum, and those
    differences would rarely be noticable in a photograph.


     
    PeterN, Apr 20, 2014
  5. Jeffery Small

    PeterN Guest

    Saved as a tiff in LAB applied curves in LAB mode to try for dark shades
    that are not in the RGB spectrum and back to RGB.

    <https://dl.dropboxusercontent.com/u/97242118/lab test.tif>

    converted the above to RGB, to LAB & back to RGB, and back to LAB
    <https://dl.dropboxusercontent.com/u/97242118/lab test rgb.tif>

    Anyone can do their own subtractions.
     
    PeterN, Apr 21, 2014
  6. Jeffery Small

    Guest Guest

    the random image was one i shot a month ago at a dance performance and
    it's not for public consumption. one performer in the image was holding
    a guitar and that is where the visible change was. there was also some
    minor differences on her clothing.

    the key is that anyone who claims converting to lab is lossless is
    mistaken.
    open image, duplicate (image/duplicate), convert to lab and back to rgb
    in the second image (image/mode) then subtract (image/calculations).
    look at the histogram to see the extent of the changes.
     
    Guest, Apr 21, 2014
  7. Jeffery Small

    Guest Guest

    it does, but what it doesn't do is convert on the fly. it *uses* lab as
    a reference. read what andrew wrote.
    that is incorrect, as explained by andrew rodney in what i quoted and
    easily demonstrated.

    converting to/from lab mode is a lossy operation. whether that matters
    to the user is up to the user to decide but anyone claiming it's
    lossless (namely dan marguilis) is mistaken.
     
    Guest, Apr 21, 2014
  8. Jeffery Small

    Guest Guest

    there's a faint line where the stitching is.

    however, to really see what changed, check the histogram (command-l).

    that stuff on the left means there's a difference and looks like it
    extends to 27 out of 255 levels. slide the white (rightmost) slider to
    the left and you can maximize just what was actually lost and it's more
    than just the stitching.

    now create a new image filled with pure black and look at its histogram
    in case you need to see what zero really means.

    aka: you are wrong.

    after that, go ask anyone on the photoshop team if a lab conversion is
    destructive. they'll set you straight. i know you don't believe me but
    maybe you'll believe one of them.
     
    Guest, Apr 21, 2014
  9. Jeffery Small

    Guest Guest

    there's a difference there too.

    i did:
    image/duplicate, append -converted to the name.
    image/mode/lab
    image/mode/rgb
    image/calculations, original on top, converted below, subtract mode

    optionally, just before the calculation step, switch between the two
    images while looking at the histogram palette. there's a difference.
    then do the calculation step.
     
    Guest, Apr 21, 2014
  10. Jeffery Small

    Guest Guest

    read what andrew rodney wrote. it uses lab internally for a reference.
    it does *not* convert from lab on the fly, as that would be slower.
     
    Guest, Apr 21, 2014
  11. Jeffery Small

    Guest Guest

    i ignored it because there is no gigo rule. tony is trolling, as usual.

    my workflow at the time was the best it could be given what tools were
    available. when new tools were released, my workflow improved. simple
    concept.

    in the future, there will be even better tools available, with a
    further improvement in workflow.
     
    Guest, Apr 21, 2014
  12. Jeffery Small

    Sandman Guest

    This is the statement:

    Eric Stevens
    Re: Any Minolta/Sony users using UFRaw and GIMP?
    04/19/2014 <>

    "Well of course he didn't actually say that. The particular
    meaning congealed from with a cloud of diffuse verbiage."

    Just how do I go about falsifying that statement, Eric? My inability to
    falsify a vague statement based on an unknown number of vague sources does
    not mean that the statement is correct.

    You made the claim, thus the burden of proof lies upon your shoulders.
    Claims doesn't become facts just because others can't disprove them.
    Indeed. I'm waiting.
     
    Sandman, Apr 21, 2014
  13. Jeffery Small

    Sandman Guest

    I haven't asked you to point to a single source. I have asked you to
    support your statement, if it requires multiple sources, then so be it.

    I'm waiting.
     
    Sandman, Apr 21, 2014
  14. Jeffery Small

    Guest Guest

    i don't know what books you've read but andrew rodney is more likely to
    be right than another book, where the authors don't know the photoshop
    team personally.
    how is that contradictory? photoshop uses multiple buffers and could
    easily have a second copy in lab in addition to rgb, or it could
    convert to lab for a specific operation.
    actually you can't. that link comes up blank here, but even if someone
    does search for a phrase or sentence to get google books (which is what
    i suspect you did), it's a session based link that is for just that
    person and will time out eventually.
    lab is device independent.
    it's certainly smaller but it's non-zero. there's no need to convert
    when a conversion is not needed.
    that book looks like it's more about algorithms rather than the
    internals of photoshop.
     
    Guest, Apr 21, 2014
  15. Jeffery Small

    Guest Guest

    you did ask why a conversion to and from lab would matter.
     
    Guest, Apr 21, 2014
  16. Jeffery Small

    PeterN Guest

    Then use a MacBeth color chart.
     
    PeterN, Apr 21, 2014
  17. Jeffery Small

    PeterN Guest

    Don't hod your breath. nospam will produce even less then Bruce.
     
    PeterN, Apr 21, 2014
  18. Jeffery Small

    Guest Guest

    andrew rodney explained it.
     
    Guest, Apr 22, 2014
  19. Jeffery Small

    PeterN Guest

    For all practical photographic purposes there is no visible differences.
    Alan Browne has posted some examples in alt.photography. I went a step
    further, using Alan's images I applied a small curve adjustment in LAB
    that should have brought some of the darker areas into a portion of the
    LAB color space that is outside the gamut of the RGB space. I converted
    the LAB image back into RGB, and saved it together with a copy of the
    LAB image. nospam was invited by both Alan And myself to duplicate the
    experiment, and has given nothing but transparent excuses for his
    failure to post a duplicable experiment.
     
    PeterN, Apr 22, 2014
  20. Jeffery Small

    PeterN Guest

    Did you expect a rational answer. He's asicaly telling you to read a book.
     
    PeterN, Apr 22, 2014
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