RGB vs sRGB Color Space

Discussion in 'Photography' started by Joel, Nov 22, 2010.

  1. Joel

    Joel Guest

    For decades I have always used RGB Color Space, and continue using it even
    I do notice that sRGB displays little brighter/richer on the web. But since
    I never care for displaying so pretty much all my software and hardware set
    to Adobe RGB color space.

    I recently (for months actually) I have run into the “The monitor profile
    appears to be defective†by Photoshop (after switching from CRT to LCD and
    Windows 7 64-bit did some upgrading, or no error report at beginning). And
    because of my poor health I haven't used Photoshop much for pretty long time
    to do more research on this issue. I do realize that the number of color
    become pretty limited (much fewer color) or the WHITE become Light YELLOW
    instead of pure WHITE.

    Few minutes ago, I switched the Monitor Color Profile from the default
    Samsung SynsMaster (whatever) to Adobe RGB (I tried the sRGB but set the
    Adobe RGB as default) and no more error report.

    While doing some research I run into the below and paste it here for
    anyone who may enjoy reading. Again, this is one man opinion, it's the only
    one I run into etc.. so NO FIGHTING -PLEASE-

    http://www.cambridgeincolour.com/tutorials/sRGB-AdobeRGB1998.htm
     
    Joel, Nov 22, 2010
    #1
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  2. ProPhoto RGB has a wider gamut than aRGB, which in turn has a wider
    gamut than sRGB. It's been available in Photoshop for quite a few years.
    And, yes, there are myriads of ways to screw up printing color-faithful.
     
    John McWilliams, Nov 23, 2010
    #2
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  3. sRGB is "good enough".
    and bigger holes between adjacent colours (and not a single
    colour more than sRGB).
    and provided your printer can print more than sRGB.
    ProPhoto
    - has many million TIMES more colours than aRGB (3 16 bit channels
    instead of 3 8 bit channels)
    - can describe almost all colours (unlike aRGB)
    - has colours which are not possible in the real world, especially
    what goes as "pure blue" and "pure green", unlike aRGB
    - is much larger than aRGB
    - can describe every colour aRGB can --- and many more

    "Kind of like aRGB" is saying a dollar is like a million
    dollars, just a bit less.

    Of course, there are quite a few more RGB colourspaces.

    -Wolfgang
     
    Wolfgang Weisselberg, Nov 27, 2010
    #3
  4. It's a shame PhotoCD died a death, since it could represent colours beyond
    RGB by allowing negative RGB values, so PhotoCD images contain colour
    information which is likely lost by most other film scanners.
     
    Gordon Freeman, Dec 5, 2010
    #4
  5. You have to think of it in terms of the individual primaries. RGB colour
    space does not encompass all colours, and by allowing negative red, blue
    green you can add CMY values which lie outside RGB colour space without
    having to explicitly represent more than three primaries.
     
    Gordon Freeman, Dec 6, 2010
    #5
  6. A film scanner can only scan what it has filters for.
    Usually, RGB (and infrared).

    Negative numbers don't give you anything that a larger space
    wouldn't give you, since you can simply use an encompassing
    colour space and translate your negative RGBs into it.

    -Wolfgang
     
    Wolfgang Weisselberg, Dec 9, 2010
    #6
  7. Yes, I am sure the scanners that Kodak used were integral to the
    process. It would not be much use using the photocd format with a
    typical retail RGB film scanner.
     
    Gordon Freeman, Dec 10, 2010
    #7
  8. Could you quote chapter and verse of the Beige Book where "negative
    RGB values" are allowed? As far as I know, the image format is
    Kodak PhotoYCC, a luminance-chrominance-chrminance model, with
    the usual 8+8+8 bits, i.e. in the range of 0..255.

    There is a transform function from YCC to R'G'B' Rec. 709 which
    can result in values outside the range of 0..255. See
    http://www.poynton.com/PDFs/ColorFAQ.pdf
    (which treats the range 0-1): "PhotoYCC extends the Rec. 709
    transfer function above unity, and reflects it around zero,
    to accommodate wide excursions of R’G’B’. To decode to
    CRT primaries, clip R’G’B’ to the range zero to one."

    Note that R'G'B' is not your linear RGB.

    That (or a similar transform into a gamut more limited than Kodak
    PhotoYCC) is probably what you mean, but in fact it only tries
    to encompass the film gamut instead of being limited to, say,
    the HDTV gamut (Rec 709, see http://en.wikipedia.org/wiki/Rec._709)
    From what I gather, they delivered high quality at the time at
    $3 per image, and were being needed by the standard.

    According to wikipedia, however, your lowly desktop scanner has
    a larger colour space and more dynamic range than the PhotoCD
    (which has only a dmax of 2.8-3.0), which caused the commercial
    system to fail in the end.
    And you'd also need special monitors to display coloure not
    available in RGB ... wouldn't you?

    In fact, the typical retail RGB film scanner would not work
    well with the photocd format, because the colour profiles
    depend on the scanner ...

    -Wolfgang
     
    Wolfgang Weisselberg, Dec 11, 2010
    #8
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