>> However, for a neutral gray
>> they (RGB) SHOULD all be the same number.
>
> no, total rubbish. the profile defines the relationship between the value
> and the actual colour output. Profiles do NOT attempt to balance the RGB or
> CMYK or CMYKOG or whatever values, they are simply the actual transfer
> functions between RGB (say) and XYZ (for example). They could be 157,23,45
> for mid grey - it doesn't matter.
>
>> Forget what Ned said about RGB
>> being device dependant (sorry Ned), that was pre Photoshop 4, when your
>> monitor profile was used as your system profile (before my time so don't
>> ask). The idea of abstract color spaces, like Adobe RGB, or sRGB, is
>> precisely that they ARE device independent.
>
> Adobe RGB and sRGB are simply attempts to define a device-independant RGB -
> which is totally pointless when you could use XYZ or even at a push LAB, but
> they are there so most other programs like image viewers and web browsers
> can simply display the images raw without any colour transformations and
> still look reasonable. Those two profiles are hopelessly compromised and
> should be avoided if at all possible. If your scanner outputs in a true
> device-independant manner, such as LAB, choose that.
>
Again, I don't know where this conversation started so I probably just don't
know what context you are talking about. For a file inside of a device
independent working space, like AdobeRGB, or sRGB, or Colormatch, R=G=B
gives neutral color. If you then Convert To Profile, and select an output
device profile, then you are right, all bets are off, that tone which was
neutral will not be neutral any longer, because it will now be converted to
a device dependant profiles description. Thus, that would NOT be a device
independent space any longer, nor would whatever tone WAS neutral before the
conversion now look neutral on screen.
The reason people don't edit in Lab is because it's an extremely unintuitive
space to work in, and while it possesses great power for strong image
correction it is not considered to be subtle enough for most common
corrections. It's certainly useable by advanced users, but even then most
users will do their common editing in more user friendly space. Some people
like to share their files in Lab space however, because it's profile
independent, thus there is less likelihood for funky conversions by users
unaware of color management issues.
Are we starting to talk the same language?
I apologize for coming into this in the middle, it surely adds to the
confusion.
Todd
>
> I've come of retirement for this one :-)
>
>> From: Todd Flashner <tflash@earthlink.net>
>
> Ned
>
>
>
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