Calibrating, Printing and Proofing by the G7™ Method

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Calibrating, Printing and Proofing by the G7 Method Version 6, August 2006 C O N T E N T S 1 Introduction ............................................................................................................ 5 1.1 About this document ............................................................................................................................................... 5 1.2 Changes to this version .......................................................................................................................................... 5 1.3 What is GRACoL 7? ............................................................................................................................................... 5 1.4 What is G7? .......................................................................................................... 6 1.5 GRACoL 7 and ISO print standards ...................................................................................................................... 6 1.6 Solving the TVI problem ......................................................................................................................................... 6 1.7 In search of international unity ............................................................................................................................... 7 2 New Variables and Definitions ............................................................................... 8 2.1 Neutral Print Density Curve (NPDC)...................................................................................................................... 8 2.2 Highlight Range (HR).............................................................................................................................................. 8 2.3 Shadow Contrast (SC)............................................................................................................................................ 9 2.4 Highlight Contrast (HC) ........................................................................................................................................ 10 2.5 HR, SC and HC aim values vs. dynamic range .................................................................................................. 11 2.6 Gray balance......................................................................................................................................................... 11 2.7 Benefits and limitations of the new method......................................................................................................... 12 2.8 When to Use TVI................................................................................................................................................... 12 2.9 G7 TVI curves and calculations ........................................................................................................................... 13 3 G7 Calibration / Profiling Summary ...................................................................... 14 3.1 Prepare the equipment and materials ................................................................................................................. 14 3.2 Print a Calibration target....................................................................................................................................... 14 3.3 Compare ‘found NPDC’ to reference NPDC ....................................................................................................... 14 3.4 Compare ‘natural gray balance’ to reference gray balance ............................................................................... 14 3.5 Calibrate the RIP or device driver ........................................................................................................................ 14 3.6 Verify the calibration ............................................................................................................................................. 14 3.7 Print a Characterization target (optional)............................................................................................................. 14 3.8 Verify the Characterization (optional) .................................................................................................................. 14 4 Time, Materials, and Tools ................................................................................... 15 4.1 Time....................................................................................................................................................................... 15 4.2 Paper ..................................................................................................................................................................... 15 4.3 Inks ........................................................................................................................................................................ 15 4.4 Test targets and images....................................................................................................................................... 15 4.5 Tools for graph paper method.............................................................................................................................. 16 4.6 Tools for software method.................................................................................................................................... 16 4.7 Dot Meter (recommended) ................................................................................................................................... 16 4.8 Hand-held spectro-densitometer.......................................................................................................................... 16 4.9 D-50 viewing conditions........................................................................................................................................ 16 5 Preparation ........................................................................................................... 17 5.1 Secure all materials .............................................................................................................................................. 17 5.2 Assemble the press form...................................................................................................................................... 17 5.3 Press control bars ................................................................................................................................................. 18 5.4 Set up the RIP....................................................................................................................................................... 19 5.5 Check plate-making system ................................................................................................................................. 19 5.6 Exotic screening or continuous-tone systems..................................................................................................... 20 5.7 Pre-adjust the plate-making system at 50% (optional) ....................................................................................... 20 5.8 Make plates for the calibration run....................................................................................................................... 20 5.9 Record an un-calibrated plate curve.................................................................................................................... 20 5.10 Check press setup.............................................................................................................................................. 20 5.11 Check measurement tools and viewing conditions........................................................................................... 20 ii Copyright © International Digital Enterprise Alliance, Inc. [IDEAlliance] (2006). All Rights Reserved.
Calibrating, Printing and Proofing by the G7 Method Version 6, August 2006 6 Calibration Test .................................................................................................... 21 6.1 Ink sequence, drying, and coating ....................................................................................................................... 21 6.2 Print to nominal solid ink values........................................................................................................................... 21 6.3 Check CMYK TVI.................................................................................................................................................. 21 6.4 Adjust device-level gray balance (optional)......................................................................................................... 22 6.5 Adjust cross-sheet evenness ............................................................................................................................... 22 6.6 Run stabilizing speed-cycle.................................................................................................................................. 22 6.7 Automated press control systems........................................................................................................................ 23 6.8 Record wet and dry ink values............................................................................................................................. 23 7 Adjusting NPDC Curves ........................................................................................ 24 7.1 Allow sample sheets to dry................................................................................................................................... 24 7.2 Measure the P2P target........................................................................................................................................ 24 7.3 Plot the curves ...................................................................................................................................................... 24 7.4 Find nearest target graph with same D-max ....................................................................................................... 25 7.5 Choose the optimum curve points ....................................................................................................................... 25 7.6 Calculate the RIP curve correction values .......................................................................................................... 25 7.7 Correcting gray balance in RIP curves ................................................................................................................ 26 7.8 Apply new aim values to RIP or CtP device........................................................................................................ 26 8 Achieving Gray Balance in RIP Curves................................................................. 27 8.1 Find the 'most neutral' patch in the C = 50% block............................................................................................. 27 8.2 Repeat for other cyan percentages ..................................................................................................................... 27 8.3 Draw new curves for Magenta and Yellow .......................................................................................................... 28 8.4 Find new aim values for Cyan, Magenta and Yellow.......................................................................................... 28 8.5 Correcting Gray Balance in IDEAlink Curve........................................................................................................ 29 8.6 Apply new aim values to RIP or CtP device........................................................................................................ 29 8.7 When NOT to apply gray balance in RIP curves ................................................................................................ 29 9 Verification/Characterization Test ....................................................................... 30 9.1 Make new characterization plates to G7 spec .................................................................................................... 30 9.2 Print the characterization target ........................................................................................................................... 30 9.3 Characterization tolerances.................................................................................................................................. 30 9.4 Confirm goal curves.............................................................................................................................................. 30 9.5 Verify gray balance and other parameters .......................................................................................................... 31 9.6 Select samples...................................................................................................................................................... 31 9.7 Measure characterization data............................................................................................................................. 31 9.8 Realistic expectations........................................................................................................................................... 31 10 Proofer Calibration and Profiling ........................................................................ 32 10.1 What proofers are compatible with G7? ............................................................................................................ 32 10.2 Workflow summary ............................................................................................................................................. 32 10.3 Qualify the proofing system................................................................................................................................ 32 10.4 Optimize the proofing system ............................................................................................................................ 32 10.5 Print the proofing form target ............................................................................................................................. 33 10.6 Measure the Press2Proof (P2P) target ............................................................................................................. 33 10.7 Plot the curves .................................................................................................................................................... 33 10.8 Align end-points at 100% ................................................................................................................................... 33 10.9 Choose the optimum curve points ..................................................................................................................... 33 10.10 Calculate the RIP curve correction values ...................................................................................................... 33 10.11 Evaluate and adjust gray balance.................................................................................................................... 33 10.12 Apply new aim values to RIP ........................................................................................................................... 33 10.13 Evaluate accuracy in neutral gray areas ......................................................................................................... 34 10.14 Evaluate match in colored areas ..................................................................................................................... 34 10.15 Solve remaining color errors via ICC profiles (if needed)............................................................................... 34 10.16 Testing ICC profiles before installing in a RIP ................................................................................................ 34 iii Copyright © International Digital Enterprise Alliance, Inc. [IDEAlliance] (2006). All Rights Reserved.
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