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62701Re: Full Write-up on Embedding the ICC Color Profile into our Jpgs

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  • sc02492
    Jul 2, 2008
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      Sorry, Freudian slip <g>:

      "With color management turned OFF, open them side by side to see if
      there is a difference, and then you can assess this more objectively."

      I obviously meant with color management turned ON. Sorry to confuse.

      Steve


      --- In ccd-newastro@yahoogroups.com, "sc02492" <sc02492@...> wrote:
      >
      > Excellent post, and I completely agree. I made the point on another
      > website that I could see no difference in my own astroimages on my
      > website (processed in sRBG space, which most of us do), whether or not
      > color management was activated in Firefox 3. Certainly for other
      > color spaces like Adobe RGB, a color managed browser would be useful,
      > but most of us don't process in Adobe RGB color space. Paul makes the
      > excellent point that tagging an astroimage in anything other than sRGB
      > color space should be avoided, since it will introduce even more
      > variability in how our astroimages appear to others, unless everyone
      > decides to use a color managed browser.
      >
      > That said, all of the images on my website are indeed tagged with sRGB
      > profiles- this has been my practice all along, the main reason being
      > that if anyone wanted to open an image in Photoshop, I wanted to
      > ensure that it looked the same to them (assuming that their monitor is
      > well calibrated). But if there is also a minor benefit to tagging an
      > image in sRGB color space, with respect to viewing it in a web
      > browser, it certainly will do no harm to include it (see end of post
      > to determine if it makes a difference for you).
      >
      > Since I cannot see a difference in astroimaging sites with color
      > management turned on or off, I'm keeping mine off for now (Firefox 3).
      > The performance hit with color management turned on, no matter how
      > small, is irritating to me since the images themselves look no
      > different on my monitor. However, I would advise people to see for
      > themselves whether astroimages on various websites look different on
      > their own monitors, and do whatever they think is best. Don't assume
      > anything until you've tried it. You can feel free to use my website
      > as a test, since I can assure you that all of the images were
      > processed in sRGB color space.
      >
      > Finally, people may find this useful to test their own system. Here
      > is one of my own images, processed in sRGB color space in Photoshop
      > but uploaded untagged:
      > http://www.starrywonders.com/rosettewithoutICCsRGB.jpg
      >
      > And here is the same image with an embedded sRGB profile tag:
      > http://www.starrywonders.com/rosettewithICCsRGB.jpg
      >
      > With color management turned OFF, open them side by side to see if
      > there is a difference, and then you can assess this more objectively.
      > Again, this may be monitor and OS dependent, so your mileage may
      > vary, but it wouldn't surprise me if most see no appreciable difference.
      >
      > Steve
      >
      >
      > Steve Cannistra
      > http://www.starrywonders.com
      >
      > --- In ccd-newastro@yahoogroups.com, Paul Beskeen <yahoo@> wrote:
      > >
      > > Hi Neil,
      > >
      > > Neil Fleming wrote:
      > > > --- Paul Beskeen <yahoo@> wrote:
      > > >> Hi Neil,
      > > >>
      > > >> 1) I don't understand what benefit you would get if
      > > >> you continue to save
      > > >> in sRGB colour space (as suggested by your workflow)
      > > >> but with "color
      > > >> profile" ticked. The default for all browsers is
      > > >> sRGB.
      > > >
      > > > Think of it this way. The sRGB color space represents
      > > > the range of values that you *can* work with. Like
      > > > the range of choices on a bingo card.
      > > >
      > > > Unless you are viewing an image with the color profile
      > > > embedded, *and* your program will accommodate that
      > > > mapping, you will see "uncontrolled" results rather
      > > > than that the author intended. "B5" on your bingo
      > > > card could be "B7" on another's.
      > > >
      > > > Just take a look at the ICC example in the original
      > > > e-mail. The authors picked (on purpose) an extreme
      > > > example, but it illustrates the point well.
      > >
      > > I don't mean to be argumentative here, and I'm certainly no expert in
      > > colour management, but I guess it comes down to the question "do ICC
      > > aware applications by default gamut map to sRGB whether or not the
      > image
      > > is tagged as sRGB?". [The default for browsers, monitors, HDTV's,
      > etc is
      > > to use sRGB colour space. Most don't succeed very well so
      > calibration is
      > > advisable for accurate display]
      > >
      > > If the person viewing your image has profiled their monitor, then the
      > > graphic card LUT tables will be set at startup to adjust to the
      correct
      > > gamma and white point. If a program is ICC enabled then in addition
      > > gamut mapping will be used to render the image's colours correctly
      > based
      > > on its tagged colour profile, or (and this may be were we differ)
      if no
      > > profile information exists in the image, as sRGB.
      > >
      > > Ahh, this "Web Browser Color Management Tutorial" page is *very*
      > > informative:
      > >
      >
      http://www.gballard.net/psd/go_live_page_profile/embeddedJPEGprofiles.html#
      > >
      > > In amongst all the other goodies it has a roll over graphic of an
      sRGB
      > > tagged and untagged image. I can discern no difference between the
      > two -
      > > so Firefox3 defaults to assuming an sRGB profile. However... when
      I try
      > > the same with Safari I can see a subtle difference! So Safari
      > doesn't do
      > > sRGB gamut mapping unless it is tagged as sRGB! From comments on the
      > > page it appears that Vista's new colour management system also
      > > automatically defaults to sRGB if an image is not tagged. Given that
      > > sRGB is the standard for the web I'm surprised that Safari doesn't
      sRGB
      > > map unless the image is tagged as such.
      > >
      > > Bottom line: Tagging as sRGB certainly does no harm and in some
      > > circumstances can lead to a more accurate rendering. Your advice is
      > > completely correct :)
      > >
      > > >> 2) If you save in an alternative colour space - such
      > > >> as Adobe RGB, then
      > > >> won't people without ICC enabled browsers see some
      > > >> very strange effects?
      > > >
      > > > I wouldn't necessarily call it "extreme", but there
      > > > would be minor differences. Adobe RGB is better
      > > > adapted to printing, with its wider gamut than sRGB.
      > > > Some of the colors would be shifted to something you
      > > > can see. What you see on your monitor would not what
      > > > would be printed, unless you have a high-end monitor
      > > > like an Eizo, one that is capable of displaying the
      > > > full Adobe 1998 gamut.
      > >
      > > Tagging images for web display with anything other than sRGB should
      > > definitely be avoided. The vast majority of web browsers are not
      colour
      > > managed & displays not profiled - an image that uses AdobeRGB or any
      > > profile other than sRGB will definitely render incorrectly.
      > >
      > > To demonstrate this issue go to the section "ADOBE RGB (1998) 2.2
      > > gamma", and try the rollover graphic.
      > >
      >
      http://www.gballard.net/psd/go_live_page_profile/embeddedJPEGprofiles.html#
      > >
      > > Cheers, Paul.
      > >
      > > > ...Neil
      > > >
      > > > www.flemingastrophotography.com
      > > > Direct from Boston - brilliant diamonds in pea soup
      > > > Also check out the astro_narrowband Yahoo group!
      > >
      >
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