Calibrating, Printing and Proofing by the G7™ Method
Calibrating, Printing and Proofing by the G7™ Method
Calibrating, Printing and Proofing by the G7™ Method
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
<strong>Calibrating</strong>, <strong>Printing</strong> <strong>and</strong> <strong>Proofing</strong> <strong>by</strong> <strong>the</strong> G7 <strong>Method</strong> Version 6, August 2006<br />
10 Proofer Calibration <strong>and</strong> Profiling<br />
This section describes how to calibrate a proofing system <strong>by</strong> <strong>the</strong> G7 method, <strong>and</strong> how to use color<br />
management (e.g. ICC profiles) to fur<strong>the</strong>r optimize <strong>the</strong> proofer's match to an official reference<br />
characterization data set like GRACoL 7 Characterization Data, or a custom ICC profile.<br />
NOTE: G7 proofer calibration is almost identical to G7 press calibration. This section is <strong>the</strong>refore a<br />
supplement to <strong>the</strong> preceding sections, with notes like '(see 7.1)' to save space.<br />
10.1 What proofers are compatible with G7?<br />
Pre-press proofing systems driven <strong>by</strong> a conventional RIP can be calibrated using a variant of <strong>the</strong> G7<br />
press calibration procedure, <strong>and</strong> <strong>the</strong>n (if necessary) color-optimized using ICC profiles or device-links<br />
for a closer match to a reference characterization data. Proprietary proofing systems with no useraccessible<br />
CMYK calibration LUTs may not be suitable for <strong>the</strong> G7 calibration, but should still be capable<br />
of a good color match to <strong>the</strong> reference characterization using ICC profiles or equivalent color<br />
management.<br />
Your proofing system may require some modification to <strong>the</strong>se instructions but <strong>the</strong> end conditions are <strong>the</strong><br />
same for any device. If your proofing system is not compatible with <strong>the</strong>se methods, ask your vendor<br />
how to match <strong>the</strong> target specifications.<br />
10.2 Workflow summary<br />
• Qualify <strong>the</strong> proofer<br />
• Print <strong>the</strong> proofing targets<br />
• Measure <strong>the</strong> Press2Proof (P2P) target<br />
• Plot <strong>the</strong> curves or load <strong>the</strong> measured data file in IDEAlink Curve software<br />
• Determine gray balance corrections (if needed) using <strong>the</strong> GrayFinder target. or <strong>the</strong> gray balance<br />
options in IDEAlink Curve<br />
• Apply correction points to <strong>the</strong> proofing RIP, if necessary with three separate curves for CMY to<br />
achieve gray balance<br />
• Test <strong>by</strong> re-printing <strong>and</strong> re-analyzing <strong>the</strong> P2P target<br />
• Create <strong>and</strong> apply ICC profiles (if needed)<br />
• Test color matching quality<br />
10.3 Qualify <strong>the</strong> proofing system<br />
Make sure <strong>the</strong> proofer;<br />
• Is stable <strong>and</strong> repeatable<br />
• Prints evenly across <strong>the</strong> whole image area<br />
• Is not subject to short-term color changes or fading<br />
• Uses a white substrate within tolerances of <strong>the</strong> target characterization or st<strong>and</strong>ard<br />
• Can yield a color gamut equal to or greater than <strong>the</strong> target characterization data<br />
• Can yield strength of black equal to or darker than <strong>the</strong> target characterization data<br />
A good way to check color gamut <strong>and</strong> dynamic range is to create an ICC profile of <strong>the</strong> proofer with color<br />
management off <strong>and</strong> compare it to <strong>the</strong> target characterization data in a utility like CHROMiX ColorThink.<br />
If <strong>the</strong> target profile is larger than <strong>the</strong> proofer profile, some colors may not proof correctly.<br />
10.4 Optimize <strong>the</strong> proofing system<br />
Optimize <strong>the</strong> proofing system following <strong>the</strong> manufacturer’s instructions, with <strong>the</strong> following exceptions;<br />
• If <strong>the</strong> instructions ask you to calibrate individual CMYK scales, GRACoL recommends omitting<br />
this stage <strong>and</strong> leaving <strong>the</strong> curve tables in an uncalibrated state, EXCEPT if <strong>the</strong> proofer provides<br />
32 Copyright © International Digital Enterprise Alliance, Inc. [IDEAlliance] (2006). All Rights Reserved.