Re: Re(3): use of sRGB as a default
Re: Re(3): use of sRGB as a default
- Subject: Re: Re(3): use of sRGB as a default
- From: Andrew Rodney <email@hidden>
- Date: Sun, 20 Jun 2004 11:59:05 -0600
on 6/20/04 11:30 AM, Matt Deatherage wrote:
>
Time out. Per my previous message, this seems incredibly vague to me. Here's
>
what I *think* you're saying:
>
>
| Untagged files in panther are assumed to be *created* in the Generic RGB
That's what John says, NOT what I'm seeing (nor Chris).
What I'm doing is saving an image untagged and opening it in Preview. I'm
also viewing it in Photoshop. IF I tag the image in Photoshop to this
Generic RGB profile, the preview in Photoshop and Preview DO NOT MATCH. If I
tag the document in Photoshop using my display profile, the two DO match. If
the untagged image in Preview were using this Generic RGB profile, then
assigning that to the same numbers in Photoshop should produce a match to
Preview. It's close but it's not a match. Assigning my display profile makes
a perfect match. So I'm confused too!
>
John has made clear, at least in my mind, that this line of thinking is not
>
good for Mac OS X. Why? "Even if the document remains untagged" is an
>
unacceptable answer - there should be no such thing as untagged images. As a
>
programmer, what I want to know is what I'm supposed to do if I find one.
With the exception of the bogus voting in Florida, I should have been
elected King of the World and my first duties would be making a law that
would disallow any untagged files <g>. Untagged files are bad, no one is
arguing that. When John says documents should be tagged, he's preaching to
the choir. That's not going to happen anytime soon so the question is, when
you get an untagged image, what do you do, what do you assume? With
Photoshop, it always assumes or knows about the document numbers. In the
case of untagged files, it simply looks at the current color settings for
each color model (RGB, CMYK, Grayscale) and uses that as the assumption. If
you have the color settings such that your RGB working space is sRGB,
Photoshop assumes all untagged RGB images are sRGB, By simply changing the
working space to Adobe RGB 1998 Photoshop now assumes all untagged RGB
images are that. This is what is supposed to be happening in the ColorSync
preferences (at least that's what it tells you when you go into that pane).
That this isn't what happens despite what the application tells you is a
royal screw-up by someone somewhere!
So despite what the preference tell you which is a big lie, the next issue
is what is being assumed? John says it's Generic RGB (whatever that's
supposed to be) and many of us are saying that's dumb, it should be sRGB (or
FIX the ColorSync utility so it does assume what you tell it. Chris however
makes a valid point that this really complicates issues for the user and I
agree).
>
If someone can explain in simple terms what to do with untagged images, as in
>
what profile to embed, almost all programs will do it once the word gets out.
What you do is tag them with the correct descriptor. The same set of numbers
can produce vastly different color appearances. You can try this in
Photoshop by making any solid color you wish with the picker and do so in
sRGB and then in Adobe RGB 1998. The numbers are not the same. They only
look the same because we have a profile for each document. Use the Assign
Profile command and give those numbers different meanings and the color
appearance changes (and the numbers don't). Which is correct?
>
If you want Preview-like programs from small developers to do the right thing
>
with profiles, it needs to be clear and simple what the right thing is.
>
Sample code is best, but a few bullet point instructions will do. If the
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answer comes back with "Photoshop 5.5" and "AdobeRGB" and "if it stays
>
untagged," they're going to punt.
While complex, Photoshop and other applications that act like it (many
working with images do) is doing the job correctly. You have an image which
is just a big pile of numbers. You either know what those numbers mean (with
a profile) or you don't (and you have to guess). It's as simple as that. The
issue isn't what you should do with images with embedded profiles. You
display the numbers based on the embedded profile. Simple. The issue is,
what do you do with, as Bruce would say, RGB mystery meat (untagged RGB)?
You either ask the user to pick a profile based on their knowing what the
tag should be, you ask them to pick until they see something that produces
acceptable color appearance or you take a big guess and don't ask the user.
There's only one "right" answer (the right tag). Right is of course open to
debate since a user ultimately has to say "I like the color appearance" or
"It's close enough but I need to change the values to produce better
appearance." But that can't really happen until the software is told what
the numbers represent and that's done by tagging/embedding/assigning a
profile.
Andrew Rodney
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