RIP Linearization Demonstration and Comparison Workshop

Transcription

1 GATF Color Management Conference 2003 RIP Linearization Demonstration and Comparison Workshop How to evaluate and validate what you calibrate ( Ways to evaluate the quality of the RIP ) Presenter: Dan B. Reid

2 What s there to check? How good was the calibration method? Can we improve (tweak) the calibration settings? How does the hue/chroma of the proofer compare to the reference print process?

3 What to do when you notice the calibration is off Check all nozzles are firing (nozzle check) Relinearize to target values

4 Problem Not all Linearization routines are the executed the same way Not all Linearization routines are successful Need to evaluate how successful the Lin process was for tonal distribution

5 Ways to Evaluate Linearization Visual: Print gradients of each primary color Create a gradient posterized into 5 or 10% increments. Use a software program to graph the results Hexagon plots 3D distribution graphing

6 So which one should I use? Visual allows for quick assessment but can t be trusted or reliably compared Analytical verifies you have achieved linear response or if further adjustment is needed

7 Quick and easy ways to check calibration Create gradients for each primary colorant (CMYK) and overprints (RGB) to verify smooth transitions Ensure separation in 10% tints increments of each colorant

8 Create your own Gradients Simple to do in Photoshop

9 So what does a Lin look like? Uncalibrated output

10 So what does a Lin look like? Calibrated state

11 So what does a Lin look like? Epson print driver

12 Bad Linearization

13 Good Linearization

14 What increments should I use to calibrate? 5, 10, 20% increments? Do you have a choice in your RIP? Can you improve the calibration by remeasuring with the Lin curve engaged? Sometime an abundance of samples points on the calibration curves can hinder linearity.

15 Correct calibration resolution

16 Incorrect Calibration Resolution

17 Ideal Scenario Ink restriction of dark primaries without LT primaries engaged Determine blending curve of LT primary to minimize hue shifting (hooking) Two pass linearization process after ink restriction Use created adjustment curves as aim values for future relinearization. Relinearize to match calibrated reference values.

18 Simple (basic) checking of calibration Measure standard color bar tints (25,50,75, 100% tints) as LAB to compare chroma/ hue to reference print color bar. Quick, only a few measurements Verify if paper/ink/calibration combination is capable of simulating the reference print process without creating an ICC profile.

19 Checking Calibrations Advanced Ink restriction hue accuracy SWOP hue versus inkjet proofer hue. Check Chroma and hue relative to reference print conditions Adjusting LT to minimize hue hooking.

20 Ink restriction, hue accuracy

21 Ink Restriction, hue accuracy

22 SWOP vs. Epson inkjet

23 Good calibration bad LT blend

24 Adjusting LT blending

25 Adjusting LT blending

26 Adjusting LT blending

27 Minimizing hue shifting in the shadows Recheck that you optimized the ink restriction for the dark colorant. Adjust LT so there is minimal shifting of the hue from the 25% down to 100%.

28 Do we really have a problem? How much tweaking do you really need to do? Do you need statistics on compliancy to reference print conditions? (SWOP/GRACOL) Verify remote proofers?

29 Validating calibration color tolerance to reference print MonacoQColor (formerly Xrite PrintCheck) ColorMetrics ProofPass

30 Trending Trending helps establish practical tolerances of color variance. Provides data for frequency of calibration (maintenance)

31 Obtain a copy of this presentation Free section

32 GATF Color Management Conference 2003 RIP Linearization Demonstration and Comparison Workshop How to evaluate and validate what you calibrate ( Ways to evaluate the quality of the RIP ) Presenter: Dan B. Reid