Re: Spectro question
Re: Spectro question
- Subject: Re: Spectro question
- From: "James B. Reswick, Jr." <email@hidden>
- Date: Tue, 3 Sep 2002 11:17:35 -0700
- Organization: Reswick Consulting
Thanks Chris!
Jim
----- Original Message -----
From: Chris Murphy <email@hidden>
To: <email@hidden>
Cc: <email@hidden>
Sent: Monday, September 02, 2002 10:33 PM
Subject: Re: Spectro question
>
>
On Monday, September 2, 2002, at 11:00 PM, "James B. Reswick, Jr."
>
<email@hidden> writes:
>
>
>
> My question is (finally): How can the profiling software know what
>
> corrections to make when comparing only the CMYK text values
>
> associated with
>
> the target's patch and the measured Lab values for that patch, when the
>
> information contained in the target's CMYK text values are relative
>
> percentages?
>
>
It doesn't. The resulting profile is just a snapshot description of how
>
a given device behaves. A single output device profile contains
>
(simplistically) two pieces of information, what CMYK values output on
>
that device look like to a person, and what CMYK values to send to the
>
device to generate a specific color.
>
>
>
> Wouldn't two device-independent coordinate descriptions for that
>
> patch (one provided and one measured) have to be available for there
>
> to be a
>
> comparison? Wouldn't an additional text file with Lab coordinates
>
> have to be
>
> provided with the target?
>
>
Effectively you get this when two profiles are combined, which is a
>
requirement for a color space conversion to occur. For color management
>
to do anything, one profile is needed to define the source space and
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another is needed for destination. The source profile effectively says
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"these RGB values mean xxxx in LAB" then the CMS uses the destination
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profile to lookup the LAB value and corresponding device values (CMYK
>
in this example) to produce that color.
>
>
The way to look at a single profile is merely as a record of how a
>
given device behaves. The profile doesn't say what corrections are
>
needed - that is up to the CMS and is determined once at least two
>
profiles have been specified (and a document to convert).
>
>
Chris Murphy
>
Color Remedies (tm)
>
Boulder, CO
>
303-415-9932
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