I just ran a test, as I wanted to test your assumption since I didn't
know either.

I found a page of my website with an image that contained fairly
bright saturated colors that I could measure and compare. I then did a
series of screen grab from Microsoft Internet Explorer on Windows, and
Safari and Firefox on Mac.

I then opened up the un-profiled jpeg (originally was sRGB if I recall)
from my site (the original file that was being displayed in the screen
grabs), and dragged and dropped it on to each of the screen grabs, and
then set the layer mode to "difference."

On the windows version, the file completely blacked out, meaning that
the color values and edge definition were exactly the same.

On both of the mac screen grabs, most of the image blacked out, though
there seemed to be issues with getting the file to line up directly on
top of each image. Thus there was a small amount of edge detail
showing. My guess is that this may be due to the slight differences in
base screen resolution between mac and windows. I'll put together a
composite of these if anyone is interested in seeing what I'm talking
about.

As a double check I used the color sampler tool in Photoshop and tried
to measure the same color patches including a few elements from the
website. Without exception, they were all within 1 or 2 RGB point
values, which I would attribute to my not being precise enough in
measuring the same area of the image. I saved these values in an Excel
spreadsheet if anyone wants to see that, just let me know.

This would be much simpler to verify with a series of color and gray
patches and that's what I would use if I was going to repeat this as
a "scientific" test.

So, unless you are talking about posting preview images that are in
another colorspace such as Adobe RGB, I don't think your assumption
holds true.

Sincerely yours,

David
--
David Riecks (that's "i" before "e", but the "e" is silent)
http://www.riecks.com , Chicago Midwest ASMP member
http://zillionbucks.com "The Webhost for your Creative Business"
Chair, SAA Imaging Technology Standards committee
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