The journey towards Universal Characterization Data (UCD)

Transcription

1 The journey towards Universal Characterization Data (UCD) 1

2 Agenda 1. Why UCDs 2. Current approaches 3. Development of Fogra characterisation data sets 4. Technical background 5. "ISO :2013+" versus "ISO " on coated paper 6. Outlook 2

3 1. Why UCDs Digital colour management solutions need characterization data Char.-data are basically CMYK LAB tables (if present, spectral data) Unified characterization data = internationally agreed upon aims are important for: unambiguous (and not regional) recommendations for print production (PDFXready, Ghent Working Group, Adobe CS Suites, etc) Easy communication of print content data across the world Reducing re-targeting (mostly DeviceLink) transformations many more 3

4 2. Current (and past) approaches WG3 meeting in Tokyo (2007) 2010, letter from David Zwang (Chairmen of GWG) toward IST TC130 Proposals: Basically char.-data that reflects the printing aims defined internationally (ISO ) or nationally (IDEAlliance, ANSI TR 21) 4

5 3. Fogra datasets Development of Fogra data: TVI Adjustment of: CIELAB Colours FOGRA1 1 Press Run FOGRA11 Averaging FOGRA27 t FOGRA39 C=M=Y ISO :2004 FOGRA51 beta C=M=Y=K ISO :2013 5

6 4. Technical background ISO approach??????? G7 calibration Creative work TR 16 approach ("G7") 6

7 4. Technical background Offset printing can be defined by knowing the solid coloration and the TVI (tone response) IDEAlliance is providing char.-data based on "G7", defined in TR 16 (CGATS. 21) since 2010 The NPDC (near neutral) definition results in char.-data where colorimetrical tone values can be extracted. The differences between "Equal-TVI" (for CMY or CMYK) ISO and Near Neutral often result in small colour differences (avg E00 <= 2) However there are printing conditions (such as non periodic, FM) where the differences are more significant There are systematic differences for some printing conditions which makes it impossible to find a consensus for all printing conditions (but not for a subset) for printing on PT1/2 the approaches can be averaged ("salomonic data") 7

8 4. ISO & ISO ("FOGRA51beta") ISO /3 correspondents Source: McDowell ISO PC7 PC5 PC6 PC2 PC1 "FOGRA39+" PC= Printing Condition 8

9 5. Comparison of CRPC6 with FOGRA51beta (2013) :2013 latest version Source: Dr. Bestmann 9

10 5. Comparison of ISO with ISO Colour differences for all 1617 patches (ISO ) 10

11 5. How to go from XYZ to densitometrical tone values? 1. Compare col. TVI with dens. TVI based from the same sample 2. Use a single scalar (value) to scale the col. TVI curve to match the dens. TVI curve 3. Analyse the values by means of different/typical substrates scalars CMYK: 1.25; 1.05; 0; 0 Dens. TVI of FOGRA39 Col. TVI of FOGRA39 11

12 5. Comparison of ISO with ISO Comparison of colorimetric TVI curves with adjustment factors estimated from ISO with its well known densitometric TVI Large differences in black. Acceptable differences in CMY process control implication: - printing condition depending RIP corrections - Colour Server 12

13 5. Differences in the black channel CRPC4 - PC6 (SC) Large TVI differences! CRPC6 - PC1 (PT 1/2) 13

14 5. Comparison: Results G7 grey balance approaches (naturally) result in higher black curves (than CMY) Equal TVI has been updated with ISO revision from C=M=Y (and sometimes higher K) to C=M=Y=K to ease process control ("one value for Dot Gain (TVI)") Differences between ISO (Equal TVI) and TR21 (near neutral) approaches can be sometimes attributed to be within typical printing variations Characterization Data should reflect a process 1:1 (no need for colour servers clut transformations) Universal exchange data shall not benefit one over the other process calibration CRPC's favour TR21 printing conditions G7 calibrated print will result in a good proof/print match (providing a CRPC6 Proof) ISO calibrated presses needs additional RIP corrections and for high accuracy a colour server Outlook Discussion 14