Re: Newsprint G7 calibration
Re: Newsprint G7 calibration
- Subject: Re: Newsprint G7 calibration
- From: Terry Wyse <email@hidden>
- Date: Sat, 24 Mar 2007 10:39:54 -0400
You SURE you used the correct target in ColorPort (there's TWO target
XML files) and you downloaded the very latest P2P package (P2P23xn
should be the correct one)? Also, you want to make sure you export
the data as CGATS with the spectral data range set to 0-100 instead
of 0-1. Haven't a clue why that is the case because as far as I know
the IDEALink software does't do anything with the spectral data but I
could be wrong.
There's nothing about the target that would make it behave
differently for newsprint vs. any other printing process assuming you
plated it as-is (no scaling or anything).
If you're going to have a chance to run the test again, I'd be happy
to send you the target that I use all the time. It's a bit wider and
shorter (5.5" x 9") than than the standard P2P target but it works
well with the DTP70 (I sized it so it's no taller than the width of a
standard DTP70 IT8.7/4 chart - makes for easier cutting up of the
press sheet!).
There WAS a problem a while back with the charts being a bit to
narrow for the DTP70 causing measurement errors but that was
supposedly fixed with the P2P23xn targets. Nonetheless, I decided to
use the supplied reference data and build my own P2P23 targets. I've
been using this target since about October of last year and on at
least 8-10 G7 press calibration jobs and it's been working fine. Let
me know if you'd like to try it. I don't easily give up my custom
targets so tell me that you're actually going to use it before I send
it to you.
FYI, I personally don't feel that the IDEALink software compensates
enough for low Dmax printing conditions such as uncoated offset or
newsprint that it really delivers on the promise of a decent visual
match between different print conditions but that's just my opinion.
The result to my eye is too dark overall and doesn't move the HR
point enough for low Dmax printing. Personally, I wish the HR
aimpoint was adjusted relative to the 100% CMY Dmax (possibly based
on a linear L* approach). As of right now, it does SOME adjustment
but not enough in my opinion.
Later,
Terry Wyse
On Mar 24, 2007, at 10:13 AM, Roger Breton wrote:
I tried my hands at calibrating newsprint using the G7 method,
yesterday.
Printed the P2P23xn target at press density. Used linear plates.
Measured
targets with DTP70 in ColorPort. Results fed into IDL : got the
weirdest
curves I ever seen. Took me a while to figure this out -- thank god
for
utilities like BabelColor's PatchTool (who provides invaluable
analysis for
any serious color work) every other row is "skipped" by the
instrument.
Bottom line, the whole test is unusable. Culprit: the design of the
target
which does not work for newsprint -- no other possible conclusions.
What to
do? Modify the P2P23xn target? Use a DTP41 to read the P2P23xn
targets in,
to salvage the test? How inconvenient. And who would have thought
of that
problem -- a priori?
_____________________________
WyseConsul
Color Management Consulting
G7 Certified Expert
email@hidden
704.843.0858
http://www.wyseconsul.com
http://www.colormanagementgroup.com
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