Digital BW, The Print

Peter

You are jumbling two different things here.  It is unfortunate that QTR ink
descriptor files seem to have been relabelled "profiles" rather than
"curves" (as has been the case with the Mac version for some time) as I
think this is cause for confusion.

The LINEARIZE function is peculiar to using Quadtone RIP.  Yes a step wedge
is printed and measured and that data is fed to QTR-Linearize-Data in order
to provide you with the function to be pasted into the ink descriptor file.
This function linearizes the L* output of the QTR greyscale.

QTR-Create-ICC PROFILES are different.  They can be used to profile the
output of a QTR curve (now poorly labelled "profiles") such as the one
completed above with the Linearize function or to profile the output of any
other greyscale workflow.  You do NOT paste anything into the ICC profile.

The ideal densities mentioned are with reference to QTR curves/profiles (not
ICC profiles).  The only thing you need remember here is that after
linearization (ie the output from an ink descriptor file including the
linearize function) a QTR curve/profile should be reasonably linear from
L*min to L*max.

If you then go ahead and QTR-Create-ICC profile that output and then print a
step wedge using that ICC profile, the pattern of density output depends on
the step wedge's document profile - and if, as is likely, it doesn't have an
embedded profile then on your workspace.  (Because two profiles are always
needed for colour management and since your printing with conversion to the
QTR ICC profile, PS needs a starting profile.  If there is none then PS
assigns, for the purposes of the conversion, your workspace.)  If your
workspace is GG2.2 you'd expect the 95 step to be printed very close to the
100 step.

Cheers

Steve


> From: Peter De Smidt <pdesmidt@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 14 Mar 2006 05:26:46 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] ICCs and linearization
> 
> The ICC I made yesterday does not come very close to the QTRs ideal
> densities.  Here are the densities, starting with the lightest:
> 
> Step      no-ICC        ICC
> 255      .05               .06
> 242      .10               .11
> 229      .16               .16
> 216      .22               .21
> 204      .29               .26
> 191      .35               .33
> 178      .43               .40
> 165      .50               .47
> 153      .57               .55
> 140      .66               .63
> 127      .76               .72
> 114      .86               .81
> 102      .97               .93
> 89         1.09            1.04
> 76         1.22            1.18
> 63         1.38            1.32
> 51         1.52            1.51
> 38         1.67            1.71
> 25         1.81            1.97
> 12         1.99            2.16
> 0           2.19            2.23
> 
> In the Eye-One folder, there's a applet QTR-Linearize-Data. Could this
> be used to make a more ideal ramp? If one inputs the appropriate text
> file, you get a text file with the LAB data plus a line on the bottom,
> such as:
> 
> LINEARIZE="96.4 92.2 86.6 82 76.9 73.1 67.6 63.6 59.3 54.4 48.6 44.6 40
> 34.4 29.8 24.1 20.5 15.9 13 9.4 5.4"
> 
> Roy says to "copy/paste this whole line into the profile file" .  Does
> this mean to paste into the ICC file?  I'm not sure how to do that, as
> Windows tells me that it can't open the ICC file.
> 
> Any help or suggestions appreciated!