[argyllcms] Re: Use of DTP-22 digital swatchbook with ArgyllCMS
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- Date: Sun, 4 Feb 2007 17:59:26 -0800
From: "Mario Becroft (mailing list)" <list@xxxxxxxxxxxxx>
Hi Mike,
A little while ago I wrote on the Argyll CMS mailing list with questions
about using the DTP-22 and you mentioned that you had one, but you had
not yet been able to achieve acceptable results with it when profiling
your inkjet and dye-sub printers.
Yes, that's my current situation. This project is on hold at the moment,
though I would like to master being able to create printer profiles. I do
use the DTP-22 for other projects, such as creating color pins for common
objects for Curvemeister:
http://www.curvemeister.com/downloads/pins/
I have now got a DTP-22 and I have just tried it out for the first time
this weekend. I have not used with Argyll CMS yet (although I intend to
try that out sooner or later) but I have been using it with the Onyx RIP
I use on my HP large format inkjet printers.
Similar situation for me - I have ColorShop, which supports a number of
operations, including basic measurements from the instrument.
So far I have calibrated my Designjet 2500CP machine using a 31 point
per colour linearisation pattern and a 500 point ICC profile pattern,
and although I have encountered a few problems, which may go away once I
become more familiar with the profiling method, the results are
initially extremely promising. The output is far better than anything I
have ever seen on my Designjet printers, and that was just my first try
with only a 500-point ICC profiling pattern (the Onyx media profiling
software recommends using 1000 or 2000 points).
That's a lot of patches! I've been making do with 180 points and no
linearization tables. Another background project of mine is to build a Lego
mindstorm gadget to read the patches - this should be relatively easy
provided the patches are assembled into a single linear strip, like a movie
film.
I had a bit of trouble setting the ink limits correctly and I think the
profile may be inaccurate in the very dark colours, but I suspect that
this might improve once I redo the ICC profile with more points and
corrected ink limit settings. I also had some trouble with the colour of
the paper, which for the media I have been testing with so far, came out
as noticably cyan, even though to the eye the media looks white.
Could be a UV issue, as Graeme says, or something else. What Lab reading do
you get for blank paper?
.....
So at this stage, this is just to say that it definitely is possible to
make useful profiles with the DTP-22, but clearly it requires some
knowledge of how best to use the tool. Once I try it out with Argyll
(which I want to use for profiling my Epson printer which does not use
the Onyx RIP) I will let you know how I get on.
I'll be interested in your experiences here.
In the Onyx media profiling software, there is a test tool which lets
you take readings with the DTP-22 and display them either as CMYK
densitometric or LAB colorimetric values on-screen. This is quite useful
for checking that the device basically works and reads colours
correctly. I imagine the Argyll system (or the colorport software you
are using) no doubt has a similar test tool.
ColorShop provides this, and a number of other functions, such as deltaE
readings. I use this a lot to compare patches from different paper and ink
combinations. The results are interesting, but not directed at generating
profiles.
I presume you have the calibration target for your DTP-22 and that you
have calibrated it? Using Onyx, after calibration it then reads the
calibration target density as 0.04 in all the channels. Before
calibration, my DTP-22 was completely wrong.
Absolutely - the target is built into the base.
I think that to test your DTP-22 and find out whether it is working
properly, the best way would be to get an IT8 target, which should come
with a sheet showing the actual colorimetric values for each point. You
can then measure these with your DTP-22 and check whether the readings
are as expected--this would clarify whether there could be a fault in
your DTP-22 or whether it is just the profiling process that is going
wrong. I intend to try this out myself just for curiousity's sake.
Great minds think alike :-) I have a Wolf Faust target, and all of the
patches that I've tested are within a few tenths of a deltaE, so I'm
confident that the DTP-22 is in good working order. I suspect that my
problem is not the patches, or the printers I'm trying to calibrate (2
inkjets, and 1 dyesub) but in how I'm using the Argyll software, or there
may be a glitch in the software that converts between ColorPort and the ti2
and ti3 files. Another thing that occurs to me after your note is that I've
ignored linearization - perhaps I need to do this as a prelude to the actual
calibration. Anyway, let's stay in touch about our experiences.
Mike Russell
www.curvemeister.com/forum/
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