[argyllcms] Newbie targen and colprof questions.
- From: Symphony Photography <symphonyphoto@xxxxxxxxx>
- To: argyllcms <argyllcms@xxxxxxxxxxxxx>
- Date: Thu, 13 May 2010 00:55:22 -0400
Hi folks,
I've been playing around with Argyll CMS to profile my printers (thanks
Graeme for all the hard work... I'm an ex-software engineer and can really
appreciate the time that went in to developing this) generating various
charts and scanning them in... basically doing some good old empirical
testing to learn the ins and outs and I have a few questions for the more
experienced folks out there.
1) colprof - When you finish generating an ICC profile it gives you a little
report such as:
"profile check complete, peak err = 17.211762, avg err = 0.458565, RMS =
0.657406"
What error does this reference and what is it relative to? I'm guessing it
can't be dE as there's no way my printer is averaging ~0.46 dE relative to
the target. What would be considered normal? If the peak error is the result
of a read error is it possible to identify which line it was from, re-read
that line and update it in the ti3 file? I know the i1 Pro isn't the most...
errrmmm... consistent tool in the world so ideally I'll be averaging several
target scans together but if one of those is bogus I'd like to correct it
before it gets thrown into the pot.
2) The targen -c argument makes reference to a "pre-conditioning" profile
but I can't find any reference as to the specifics of what a
pre-conditioning profile is other than that it is an icc profile (which is
what the argument takes as an input). Is it any old icc profile previously
built for a printer/driver/paper combo or is it something specific?
3) I've been experimenting with various settings for target, and profile
generation but I'm having trouble with some of the mid-tones and shadows.
I've noticed this on a few different types of paper with both a Canon
IPF6100 and an IPF8300. Using the Bill Atkinson test page as an example if
I'm measuring a spot on the strawberries which reads 126,0,0 the profile
generated by Argyll will shift that to something significantly brighter. I
do not see this happening with using the 918 patch Bill Atkinson chart read
via the Measure Tool and converted using Eye One Match. This is clearly
visible on a Granger Chart as well. I don't think it's the instrument (i1
Pro) as I've used it with Eye One Match reading in the 918 patch Bill
Atkinson profile via the measure tool and density is fine (with the
exception of highlights, especially in the yellows). I'm pretty sure it's
just a matter of generating the right target (PEBKAC error.... Problem
Exists Between Keyboard And Chair) but I'm not sure where to go yet. Another
issue I'm having is with the specular highlights in the orange fall foliage
scene (in the first column of the Atkinson test image). The profiles I've
generated so far with Argyll seem to do away with all the specular
highlights, the result of which is a seemingly less detailed shot. Another
issue I'm seeing is certain areas of the profile that seem to have "waves"
of posterization although I'm pretty sure it's not posterization, it seems
to be in the profile. I know that when I was generating the ICC profile with
my initial tests with 462 path targets it was quite bad but introducing the
-qu argument in colproof went a long way to eliminate that.
4) Just an observation - When using the i1 Pro to read targets, I've noticed
that I get a rather high dE from one scan to another when comparing
measurement files when using the Measure Tool. I was kind of surprised by
this as it's somewhat counter-intuitive to me. I figured that a slower scan
across the strips would result in more samples which would result in better
averaging and more consistent results but that seems to not be the case.
With Argyll however it is... if I scan as fast as I do with the measure tool
the reading will almost always fail. Argyll seems to like a REALLY slow scan
across the strips (fwiw I have the most recent version of hardware (just
bought it) so the sampling frequency should be rather quick).
5) Is it possible for Argyll to report DMax, and DMin either from doing a
few spot measurements or from an existing scanned target???
Finally... here's the commands I've used:
targen -v -d2 -G -g256 -e32 -f2310 test_d2_G_g128_e32_f2310
printtarg -ii1 -T -pLetter test_d2_G_g128_e32_f2310
chartread -v -H test_d2_G_g128_e32_f2310
colprof -v -qu test_d2_G_g128_e32_f2310
If anyone wants to build the ICC profile the ti3 file is here:
http://www.symphonyphoto.com/argyllcms/ArgyllTestFiles.zip
2310 patches is most likely overkill for this machine but as I said I'm
experimenting at the moment to see what is/isn't worth spending the time on
for when I go to build a bunch of profiles. FWIW this specific
printer/driver/paper combo is a Canon IPF6100 using the Photoshop plugin at
16 bits with Epson Enhanced Matte paper. The profile is already smoother
than what I was getting with the Atkinson Charts, Measure Tool, and Eye One
Match but I'd like to refine it even more. If anyone has any suggestions I'd
love to hear them.
Cheers, Joe
--
Symphony Photography
http://www.symphonyphoto.com
Other related posts:
