iarigai lanat communication on visual perception and colour management montreal presentation 2010

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Iarigai lanat communication on visual perception and colour management montreal presentation 2010

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  • 1. Visual Perception and Colour ManagementLuc LANAT, Anna NICANDER iarigai Montreal Sept. 2010

2. iarigai Montreal Luc LANAT Sept 2010 2Summary Why are we here ? Misunderstandings to clarify. Study 1. Whiteness panel ranking of European commercial papers, indoor butNordic light. Study 2. ISO12647-2 targets and evaluation of Colour Gamut at full tones inHeat Set Web Offset MWC papers from European market 2009. Study 3. Gravure trial 2010 at industrial printer to compare LWC and LWC highbrightness from same mill. Link with Standardization and Conclusions. 3. iarigai Montreal Luc LANAT Sept 2010 3Why are we here ? Communication within the value chain of paper-print:visual perception and colour management on commercial publication papergrades. Printed media efforts must concentrate on what they do best: offering emotions. Emotions and quality images are linked. We need: Optical paper measurements to match visual perception with human eye inusual home-office conditions. Quantify paper performance when evaluating colour coordinates of theCMY-RGB hexagon. Encourage further standardization developments. 4. Misunderstandings to clarify1/2 Misunderstandings due to differences between printing equipments andpapermaking equipments. Geometry 45/0or 0/45versus papermakers d/0. Calibration routines existing in papermaking, not in printing. Misunderstandings due the differences in lighting conditions betweenpapermakers and printers. Papermakers use D65 illuminant mostly Xenon light sources. Printers use D50 illuminant for historical reasons (Jordan, 2006). CIE illuminant, ID65 (indoor D65), Nordic daylight behind a window, addsiarigai Montreal Luc LANAT Sept 2010 4confusion. WCIE C2close to WCIE ID 65 ?? 5. Misunderstandings to clarify2/2 Misunderstandings between colour management prepress specifications andvisual perception of white paper colour. White point of paper is needed as a zero point for colour managementsoftware and characterization data. The visual aspect of white paper is a different concept than paper colourmeasurement needed for colour management settings. Misunderstandings on printing relevant properties. Which paper properties are relevant for paper during printing? Misunderstandings motivated by different interests between stakeholders. Value-chain not technically talking much.iarigai Montreal Luc LANAT Sept 2010 5 6. Methodology and equipments Elrepho spherical spectrophotometer (d/0), availab le in paper industry. Routines are available to measure Colour L*, a*, b* D50, with the UVcalibration of C illuminant. See ISO 5631-3. i-one X-Rite angular spectrophotomer (45/0) used in graphic industry foriarigai Montreal Luc LANAT Sept 2010 6printing evaluations. Printing trials HSWO and Gravure. Most parameters kept constant, and concentrated on paper changes. Target ink densities typical for coated and uncoated papers. Inks were industrial inks. HSWO trials printed at KCL pilot plant in Finland. Gravure trials at industrial printer in France. 7. 1. Whiteness panel, indoor but Nordic lightMethods Visual panel for paper whiteness perception. 12 experienced people to rank papers from Improved News up to WFC (Woodiarigai Montreal Luc LANAT Sept 2010 7Free Coated) Test operated in Falun mid-Sweden indoor but behind a window under noonovercast Nordic daylight. Compare ranking with optical laboratory properties : Brightness D65, C Brightness, Whiteness, Colour L*a*b* 8. 1. Whiteness panel indoor, but Nordic lightResults 1/3SC A+ 56 gsmLWC 54 gsmSC A ++ 51 gsmWF Silk 115 gsmMWC 80 gsm100908070605040302010iarigai Montreal Luc LANAT Sept 2010 8 VisualWhitenessperceptionunder indoorconditionsbut Nordicovercastdaylight,papers in x-axisin orderof visualranking.Whiteness-Brightness scale on left, Fluorescence scale on right.110100908070605040SC A 56 gsmImproved News 52 gsmSC A 56 gsmOffset News 52 gsmSC A 56 gsmLWC 57 gsmLWC 57 gsmImproved News 52 gsmImproved News 52 gsmSC A++ 57 gsmSCA++ 57 gsmLWC 57 gsmLWC 70 gsmMWC 70 gsm0Fluorescence, D65/10 D65-Brightness CIE-Whiteness, C/2 9. 1. Whiteness panel, indoor but Nordic lightResultats 2/31101009080706050SC A 56 gsmImproved News 52 gsmLWC 57 gsmSC A+ 56 gsmLWC 54 gsmSC A ++ 51 gsmMWC 80 gsm100908070605040302010iarigai Montreal Luc LANAT Sept 2010 9 Whiteness C valuesfrom 40 to 110. D65 Brightness valuesfrom 60 to 95. Whiteness is thusmore distinctive. Papers at sameBrightness D65 do showdifferences whenmeasured withWhiteness C. Whiteness C more inaccordance with visualranking. Preferred !Whiteness-Brightness scale on left, Fluorescence scale on right.40Offset News 52 gsmSC A 56 gsmSC A 56 gsmLWC 57 gsmImproved News 52 gsmImproved News 52 gsmSC A++ 57 gsmSCA++ 57 gsmLWC 57 gsmLWC 70 gsmMWC 70 gsmWF Silk 115 gsm0Fluorescence, D65/10 D65-Brightness CIE-Whiteness, C/2 10. 1. Whiteness panel, indoor but Nordic lightResultats 3/31101009080706050SC A 56 gsmImproved News 52 gsmLWC 57 gsmSC A+ 56 gsmLWC 54 gsmSC A ++ 51 gsmMWC 80 gsm100908070605040302010iarigai Montreal Luc LANAT Sept 2010 10 Whiteness values > 60: Whiteness C closermatch than D65Brightness. Whiteness values < 60: Shade andFluorescencedominates. Visual evaluations differdue to shade at lowerwhiteness. Whiteness calculationformula integratesshade. b* shade and L* aremost influent onWhiteness.Whiteness-Brightness scale on left, Fluorescence scale on right.40Offset News 52 gsmSC A 56 gsmSC A 56 gsmLWC 57 gsmImproved News 52 gsmImproved News 52 gsmSC A++ 57 gsmSCA++ 57 gsmLWC 57 gsmLWC 70 gsmMWC 70 gsmWF Silk 115 gsm0Fluorescence, D65/10 D65-Brightness CIE-Whiteness, C/2 11. Colour Management-Colour Gamut calculationC-120 -80 120A Kppers 7-colourB gravure on coatediarigai Montreal Luc LANAT Sept 2010 1112040-80-120a*b*ABFEDReminder 1/4Schlpfer (2000)C offset on coatedF newspaper(CSWO)Gamut categories forprinting processesSchlpfer (2000) 12. Colour Management-Colour Gamut calculationReminder 2/4 Larger colour gamut, or colour range commonly accepted as better print quality. Kurt Schlpfer (2000) suggested to evaluate the chroma (saturation) values ofprimary colours - Cyan C, Magenta M, Yellow Y -and the secondary colours -Red (M+Y), Green (C+Y) and Blue (C+M). One single number, the gamut area in the a* b*-plan : Chroma sum (C* Sum)with 6 primary and secondary colours.6( ) ( ) =2 2= +* C Sum a b1n*n*niarigai Montreal Luc LANAT Sept 2010 12 NOTE : 50 units in Chroma sum to identify different categories. L* coordinate not included in calculation. 13. Colour Management-Colour Gamut calculationReminder 3/4 Internal study Stora Enso Press Selection grades printed in rotogravure. Results were in line with usual paper classification. Ranking from low to high Colour Gamut in a* and b* plane: Improved News 52 gsm, White Improved News 55 gsm, SC B 56, SC A 56gsm, SC A+ 56 gsm, SC A ++ 54 gsm, LWC 54 gsm, LWC 57 gsm, LWC +70 gsm. Close to L* coordinate ranking, thus study further the a* and b* plane, asan approach to colour gamut evaluation.iarigai Montreal Luc LANAT Sept 2010 13 14. Colour Management-Colour Gamut calculationa*b* coordinates of rotogravure prints Reminder 4/4100806040200-80 -60 -40 -20 0 20 40 60 80-20-40-60Kv ExoPress 52Su SilvaPress 55Lg EnviPress 56MX EnviPress 56Kv PubliPress 56Mx PubliPress 56Su MagniPress Bulky 56Re InnoPress 54Ka Neo G 57 (54?)Co Neo G 57Co Terra G 70iarigai Montreal Luc LANAT Sept 2010 14 15. 2. HSWO printing. 12647-2 and Colour GamutMethods Printing HSWO MWC papers from 70 to 115 gsm European market. Position the colour gamut variations versus ISO-ECI-FOGRA targetsdescribed in characterization data. Evaluate colour gamut to rank papers with possible links to paperiarigai Montreal Luc LANAT Sept 2010 15properties. Pilot plant under consistent conditions. Web 130c onstant. Target densities: Black 1,70 / Cyan 1,50 (+/-0,05) / Magenta 1,30 / Yellow1,20 and kept constant for all grades. Target densities were not optimised to reach CIELAB values for primaryand secondary colours as specified in ISO 12647-2. 16. 2. HSWO printing. 12647-2 and Colour GamutResults 1/5Full circle = tolerances of ISO 12647-2, center on target.Dotted circle = tolerances of ISO 12647-2, center on average of all papers.Paper Black20151050-5-10-15-20All papers ISO12647-2 (1&2)-20 -15 -10 -5 0 5 10 15 20All papers ISO12647-2 (1&2)iarigai Montreal Luc LANAT Sept 2010 1620151050-5-10-15-20-20 -15 -10 -5 0 5 10 15 20 17. 2. HSWO printing. 12647-2 and Colour GamutResults 2/5Full circle = tolerances of ISO 12647-2, center on target.Dotted circle = tolerances of ISO 12647-2, center on average of all papers.Cyan Magenta20151050-5-10-15-20All papers ISO12647-2 (1&2)50 55 60 65 70 75 80 85 90All papers ISO12647-2 (1&2)iarigai Montreal Luc LANAT Sept 2010 17-30-35-40-45-50-55-60-65-70-60 -55 -50 -45 -40 -35 -30 -25 -20 18. 2. HSWO printing. 12647-2 and Colour GamutResults 3/5Full circle = tolerances of ISO 12647-2, center on target.Dotted circle = tolerances of ISO 12647-2, center on average of all papers.Yellow Red (M+Y)706560555045403530All papers ISO12647-2 (1&2)50 55 60 65 70 75 80 85 90All papers ISO12647-2 (1&2)iarigai Montreal Luc LANAT Sept 2010 18110105100959085807570-20 -15 -10 -5 0 5 10 15 19. 2. HSWO printing. 12647-2 and Colour GamutResults 4/5Full circle = tolerances of ISO 12647-2, center on target.Dotted circle = tolerances of ISO 12647-2, center on average of all papers.-30-35-40-45-50-55-60-65-70All papers ISO12647-2 (1&2)5 10 15 20 25 30 35 40Green (C+Y)All papers ISO12647-2 (1&2)iarigai Montreal Luc LANAT Sept 2010 1945403530252015105-85 -80 -75 -70 -65 -60 -55 -50 -45Blue (C+M) 20. 2. HSWO printing. 12647-2 and Colour GamutComments Variation tolerances allowed in 12647-2 are reached. They are rather wide andeven allow papers ranging from LWC 70 gsm up to WF 115 gsm, Silk andGloss to be within the tolerances allowed by the standard. ISO targets (see figure 2a tests on blank Paper) differ from avera

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