RE: Black generation questions for large format inkjet
RE: Black generation questions for large format inkjet
- Subject: RE: Black generation questions for large format inkjet
- From: email@hidden
- Date: Thu, 19 Apr 2007 16:37:29 -0400
On 18-Apr-07 23:49 Lorenzo Ridolfi wrote:
>Ok. I didn't explained that I'm generating a custom testchart using
>my separation settings. Using a testchart with the same separations
>settings I believe I may have a better profile, as I'm measuring
>colors that are very similar to the ones in the PCS->CMYK tables in the
>future profile.
>Ok. I know I'm being a lot perfectionist. Maybe a intermediate option is
>to generate a testchart using the right GCR setting and "play" with
>black limit, black width and black start.
While your intentions are laudable your method in generating testcharts
will probably degrade the profile derived from it. The role of
characterization data is to be representative of system performance; i.e.
given this stimulus what is the innate system response. For a printer,
known inking values (CMYK’s) are the stimulus and the resultant measured
colors (XYZ/Lab) is the response. This brings up the subject of system
Calibration versus Characterization. The innate system response is
affected by Calibration: the steps required to bring the system to a
desired and known state. Once this is done, then printing and measuring a
test chart serves to Characterize the system and it is this latter data
that all profile generation apps utilize to build a Profile.
So with respect to your inkjet printer, you should calibrate the device
first, but no Profile should be used in generating the testchart data. To
do so obfuscates the innate system response. As pointed out earlier, a
single valid characterization data set serves to generate many Profiles
which differ in UI parameter settings.
My recommendation for ProfileMaker settings would be as follows:
Max Black = 100%
Black Start = 30%
TAC = 360
K-curve shape = medium GCR
BlackWidth = 0 <minimal amount of K off neutral axis>
For the same set of separation settings, PM5 profiles typically generate
less Black than say Monaco or other profile gen applications. The above mix
of parameters ensures that you maintain a maximum dynamic range on neutral
while minimizing the amount of K injected off-axis. You may want to try a
range of BlackWidth settings – your concern about squeezing the color-life
out of yellows strike me as being quite valid.
Harold Boll
TOSHIBA AMERICA BUSINESS SOLUTIONS 2 Musick, Irvine, CA 92618
Harold Boll | 1.781.856.5174 | email@hidden
" The sunlights differ, but there is only one darkness. "
Ursula K. Leguin
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