Re: Spectro question - try again
Re: Spectro question - try again
- Subject: Re: Spectro question - try again
- From: bruce fraser <email@hidden>
- Date: Tue, 3 Sep 2002 13:30:04 -0700
At 2:45 PM -0500 9/3/02, email@hidden wrote:
James Reswick Jr. asks some interesting question and received several
answers - which - IMHO all missed the point he was driving at. This still
leaves a good question on the table. Let me restate his questions the way I
understand it, and see if there are any takers.
If the data (in the target) being sent to the output device for profiling
is CMYK numbers, and the data being captured by the measuring device is LAB
space numbers, how can the profile building software compare these two
different types of numbers in a meaningful way?
The reason to build the profile is to find out what color (Lab) you
get when you send a particular set of CMYK values. Device profiles
correlate the stimulus -- the control signals -- the RGB's and CMYK's
-- with the response -- the actual colors -- the Lab values -- that
the device produces in response to those stimuli.
He goes on to ask if the numbers used for both steps (target printing and
measurement) should be the same type of numbers (device-independent
coordinates) in order to facilitate a comparison during the building of a
profile.
Printers don't print with L* a* and b* colorants. They use CMYK
(usually) inks. You HAVE to find out what colors the different ink
mixes produce before you can do anything else. A profile simply
describes the colors that different ink mixes produce on the paper
stock in question..
Or, if the two are not the same type of numbers, shouldn't there
be another file for the output that cross references the print values with
Lab values? This would then allow the Lab measurements to be easily
compared to the Lab references for output.
What Lab references? The profile IS the file that cross references
the print values with the Lab values.
Bruce
--
email@hidden
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