sGray Profile

Discussion in 'Photoshop Tutorials' started by Alan Smithee, Aug 23, 2005.

  1. Alan Smithee

    Alan Smithee Guest

    What is the sGray profile used for under color settings Working Spaces |
    Gray ?
     
    Alan Smithee, Aug 23, 2005
    #1
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  2. It is grayscale working-space profile that has the same transfer
    function that the sadRGB RGB working-space profile has.

    It is sensible to use such a grayscale working-space profile that has
    the same transfer function that the current RGB working-space profile
    has. Othervice e.g. the individual channel views are not corect.

    TImo Autiokari
    http://www.aim-dtp.net/
     
    Timo Autiokari, Aug 24, 2005
    #2
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  3. Alan Smithee

    Alan Smithee Guest

    What's sadRGB? By transfer function you mean a curve or like the transfer
    function in the print dialogue?
    So in practical terms how do I use it? With RGB images that I want to
    convert or work on in Black & White?
    Thx.
     
    Alan Smithee, Aug 24, 2005
    #3
  4. Alan Smithee

    Bill Hilton Guest

    What's sadRGB?

    sRGB ... while officially "s" stands for "standard" (at least HP and
    Microsoft wish it were standard) to Timo and many others used to wider
    spaces it can also signify "sorry", "sad", "small" or "shi**y :)
     
    Bill Hilton, Aug 25, 2005
    #4
  5. Yes, due to historical technical reasons many RGB spaces are
    non-linear, namely they have transfer function that has the form of a
    power function, it is also called as gamma. Gamma 2.5 is the transfer
    function of the CRT monitors. In Mac systems the image data is by
    default adjusted by the operation system by gamma 1/1.45 so the
    effective gamma of Mac systems with CRT monitor is 2.5*(1/1.45)=1.72
    but due to a fault in a historical tool (The Mac gamma tool) it was
    said to be 1.8. The very same fault (by the very same author) was there
    in the Gamma tool that the Windows version of Photoshop had up to v
    4.0.1, therefore the gamma in default PC systems is said to be 2.2
    while it in reality is gamma 2.5 since Windows operation systems by
    default do not adjust the data that goes to monitor at all.

    sadRGB (sRGB) has a transfer function that is not a gamma gamma
    function, this has the effect that there will be more color error when
    the image is edited sadRGB color-space than what there are when the
    image is edited in an accurate gamma 2.2 color-space. sadRGB has the
    gamut (primaries or phosphors set) named as the HDTV, there are no
    display systems that have these primaries, the vast majority of CRT
    monitor have primaries that have the name Trinitron (this does not have
    anything to do with the mask technology that also is called as
    Trinitron). Due to this gamut issue sadRGB images that you see on the
    Web often have slight reddish or magentaish cast. So, sadRGB really is
    not good at all for Web publishing.
    Photoshop is automatically using the current RGB and grayscale
    working-space profiles. So when you convert from RGB to Grayscale then
    it is converted from the current space that the image has to your
    grayscale working-space profile. Also the individual channel views are
    shown using that gray profile.

    If you work in an other RGB working space than the sadRGB then it is
    sensible (necessary) to change also the Gray working space profile,
    e.g. if you work in a linear RGB working space then open the
    Edit/ColorSettings dialog, there open the Working Spaces Gray dropdown,
    select the second item from the top of that list (Custom Gamma) and
    enter the value 1.0 to that dialog. If you insist to work in a
    non-linear RGB working-space like the adobeRGB then do the above but
    enter the value 2.2 to the custom gamma dialog.

    Timo Autiokari
    http://www.aim-dtp.net/
     
    timo.autiokari, Aug 25, 2005
    #5
  6. Alan Smithee

    madum_tv

    Joined:
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    hello,
    i have a similar issue.
    i shoot with a canon reflex.
    My printer is an hp (5540) and i use windows and photoshop.
    When i try to print, i can only print my photo in SGray profile, i can't change it.
    I don't find any solution to fix this kind of issue.
    Do you have a link to a tutorial to solve this?
    Thanks !
     
    madum_tv, Nov 17, 2021
    #6
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