[Lcms-user] Re: thanx and query.

[<ma...@li...>]

Hi,

> Thanx for making this stuff available. I have been trying to get a handle
> on ICM WRT modifying a epson inkjet profile for use with a 3'rd party ink
> (enhanced generations). I've spent the weekend reading specs and stuff but
> I'm not sure I quite have it.
> The profiles I'm interested in seem to have both RGB to PCS and PCS to RGB
> conversion tables (epson printers take RGB not CMYK). If both tables are
> used by the CMM it seems to defeat the point of using the PCS - you still
> need one profile per input-output combo?

Think about profiles as a abstract representation of colorspace, no matter
how are they built internally. If you take a profile of your epson inkjet, this
is a representation of the particular RGB space of that printer.

So, if you want to print, for example, a image that is in sRGB space, you
need to convert from sRGB to the epson inkject RGB space in order to keep
original colors.

And that is the job of the CMM. It converts between colorspaces.
No more, no less.  If you use same profile on input and output... well, you
are converting form your inkjet colorspace to your inkjet colorspace.
No changes at all.  This is the reason why the CMM does need at less
two profiles.

> I would have expected the CMM to need a pair of profiles?

You need a pair of *different* profiles in order to get meaninfull results.
You need to know the colorspace of the image in order to print it
accurately. This is the function of embedded profiles, or the sRGB space.
sRGB is a "reasonable default" when you have not any information on
which space the image is.

> Your profile viewer has been very useful, I'm about to play some of your
> other programs. My plan is the print 16^3 test patches using OEM ink and
> try to match as far as possible the new ink. The archival ink is much
> colder in the yellow and magenta.

Unfortunately, we have still no printer profiler available. We are working on this
stuff, but is harder that it seems. I do expect to have a prototype in middle of
next summer. Meanwhile, you have free scanner & monitor profiles in site.


Regards,
Martí Maria
The little cms project
http://www.littlecms.com
ma...@li...

----- Original Message -----
From: "Eddie Matejowsky" <ed...@op...>
To: <in...@li...>
Sent: Sunday, February 17, 2002 9:48 PM
Subject: thanx and query.


> Hi,
> Thanx for making this stuff available. I have been trying to get a handle
> on ICM WRT modifying a epson inkjet profile for use with a 3'rd party ink
> (enhanced generations). I've spent the weekend reading specs and stuff but
> I'm not sure I quite have it.
> The profiles I'm interested in seem to have both RGB to PCS and PCS to RGB
> conversion tables (epson printers take RGB not CMYK). If both tables are
> used by the CMM it seems to defeat the point of using the PCS - you still
> need one profile per input-output combo?
> I would have expected the CMM to need a pair of profiles?
> Your profile viewer has been very useful, I'm about to play some of your
> other programs. My plan is the print 16^3 test patches using OEM ink and
> try to match as far as possible the new ink. The archival ink is much
> colder in the yellow and magenta.
> My motto of "they're only numbers - how hard can it be" is going to tested.
> Ciao Eddie.