RE: [APML] Again! Gamma Cygni Re-reprocessed

[astropix@att.net (Geoff Powers)]

 Nicola writes:
> I'd like to hear from someone else about embedding colour
> profiles....what do you guys out there think about it?

 Hey Nicola...

     Jerry Lodriguss first brought these 'color space' and 'color managed workflow' 
issues to my attention, right here at APML. His posts are in the archives, somewhere.

     Following his lead, I researched the matter further, and this is what I learned:

     Identical RGB values are reproduced differently on different display
devices. Lotsa variables across a multitude of hardware/software platforms. sRGB
is the M$ Windoze 'default' color space... primarily intended for those Windoze
users with no advanced image editing programs.(e.g. Photoshop, Picture Window
etc.)

Consequently, sRGB has become the 'default' color space of the Internet at
large. I have the latest versions of IE, Netscape, Opera, and Mozilla... sRGB is
the *only* embedded color profile *any* of these browsers recognize.

Without this embedded profile, browsers (and often servers) use relatively crude
algorithms to code/decode, compress/decompress and convert color space for image
file color data. Color mapping in sRGB space with an advanced image editor
assures a higher level of output quality, opposed to the more simplistic
server/browser code functions.

sRGB is a very low gamut color space... but this is by design. Due to
differences in hardware/software CLUTs, DAC nonlinearity, differences in monitor
phosphors, monitor gamma, etc., the same image might look very different on a
Mac than on a Windows box or an SGI workstation. The greatest culprit in
accounting for these differences is individual system gamma. sRGB lowers color
data to levels that will cover most of these differentials.

Carefully processed images will typically show little (if any) change after
sRGB conversion... as far as web display is concerned. In fact, if web display
is your only concern, you should make sRGB your 'Working' color space!

However, if you desire to make high quality prints, either by yourself or
through a pro color lab... a higher gamut color space is necessary, to take full
advantage of all color possibilities, in both acquisition and print out mediums.

Conversion to sRGB should be among the *last* steps you take in processing an
image for Web display when using a high gamut 'Working' color space... in order
to preserve the maximum integrity of the original image. I typically have two
versions of each image file headed for web display... one hi-res TIFF for print
quality in 'Working' color apace -- one compressed JPEG for web publication in
sRGB color space.

Long story short, if you assign 'Working' color space (e.g. RGB Adobe '98) prior
to any processing steps, then convert to sRGB as a final step, your Web images will
closely match your full-res files. Not only this, but everyone viewing your images
will see what you intended them to see... the images will display more uniformly
across the Internet at large!

 Hope This Helps...   :o)

--
 Geoff

http://home.att.net/~astropix/


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