Calibrating, Printing and Proofing by the G7™ Method
Calibrating, Printing and Proofing by the G7™ Method
Calibrating, Printing and Proofing by the G7™ Method
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<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 />
7.4 Find nearest target graph with same D-max<br />
Find <strong>the</strong> target graph nearest to <strong>the</strong> D-max (Maximum Neutral density) of your graph. If your device is<br />
not close to any of <strong>the</strong> pre-printed graphs, use <strong>the</strong> two nearest graphs (higher <strong>and</strong> lower D-max) to<br />
assist in re-drawing a new reference graph that parallels its neighbors <strong>and</strong> precisely meets your device<br />
curve at 100%.<br />
Finding <strong>the</strong> target graph that meets your sample graph at 100%<br />
7.5 Choose <strong>the</strong> optimum curve points<br />
Examine <strong>the</strong> graphs <strong>and</strong> decide how many 'curve points' are<br />
needed - typically wherever your curve bends significantly.<br />
For example, <strong>the</strong> curve at right requires points at 2% <strong>and</strong><br />
15%, <strong>and</strong> ideally at 10% <strong>and</strong> 20%, for maximum accuracy.<br />
The green line shows how profiling software falsely interprets<br />
real performance (red) from 10%-spaced data (blue) unless<br />
extra curve points (circled) are added.<br />
NOTE: Some RIPs require specific curve points. Fewer points may reduce <strong>the</strong> chance of b<strong>and</strong>ing, but<br />
extra precision is often needed in lighter tones.<br />
7.6 Calculate <strong>the</strong> RIP curve correction values<br />
For each curve point on <strong>the</strong> graph paper (or curve points for your RIP) do <strong>the</strong> following:<br />
• Draw a vertical line UP to meet <strong>the</strong> target graph.<br />
• From <strong>the</strong>re draw a horizontal line ACROSS (left or right) to <strong>the</strong> device graph.<br />
• From <strong>the</strong>re draw a vertical line DOWN to <strong>the</strong> bottom axis to get <strong>the</strong> 'new aim value.' Record that<br />
in <strong>the</strong> 'new aims value' column on <strong>the</strong> graph paper.<br />
• Repeat for each curve point except 0% <strong>and</strong> 100%, which never change.<br />
25 Copyright © International Digital Enterprise Alliance, Inc. [IDEAlliance] (2006). All Rights Reserved.