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62703Re: Full Write-up on Embedding the ICC Color Profile into our Jpgs

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  • sc02492
    Jul 2, 2008
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      Neil, that's a good question- I don't know, but if you look at the
      size difference between the embedded versus non-embedded image, it is
      minor. So perhaps it's some sort of processing/interpretation of the
      ICC profile?

      Steve

      --- In ccd-newastro@yahoogroups.com, Neil Fleming <neilfleming@...> wrote:
      >
      > I see only subtle differences on my current monitor,
      > Steve. I suspect that would change from
      > monitor-to-monitor, though.
      >
      > I wonder if the "perfomance impact" is due to some
      > additional download requirements due to the profile
      > being embedded, or to the interpretation of the ICC
      > profile once downloaded. The former, I would guess.
      >
      > ...Neil
      >
      > --- sc02492 <sc02492@...> wrote:
      >
      > > 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.
      > >
      > === message truncated ===
      >
      >
      > www.flemingastrophotography.com
      > Direct from Boston - brilliant diamonds in pea soup
      > Also check out the astro_narrowband Yahoo group!
      >
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