Colour gamut reduction over time in a coldset process

Transcription

1 Colour gamut reduction over time in a coldset process What are its implications? Manfred Werfel Deputy CEO Executive Director Newspaper Production WAN-IFRA GmbH & Co. KG

2 Colour in coldset ofset We talk much about colour quality Everybody wants to get more colour quality But colour quality is limited by the underlaying basics of the printing proces 2

3 Paper is made from natural ressources Source: ISO Focus, February

4 Ink on paper isn t it simple like that? 4

5 Thickness of ink film on paper Ink film, 1 µm Paper, 70+ µm 5

6 Ink on paper not so simple at all Ink film, 1 µm Coating Paper, 70+ µm WOCG Guide, December 2001 Source: WOCG Guide, December

7 How much ink on a newspaper copy? How much ink do need to print: One newspaper copy 48 pages broadsheet Full colour, 4c 5 g 0, g per page 7

8 LWC = Light Weight Coated WOCG Guide, December 2001 Source: WOCG Guide, December

9 LWC = Light Weight Coated Ink film Ink penetratio nink film Ink penetration Coating Coating Hole Hole WOCG Guide, December 2001 Source: WOCG Guide, December

10 SC = Super Calendered Ink Paper WOCG Guide, December 2001 Source: WOCG Guide, December

11 NP = Newsprint Ink Paper WOCG Guide, December 2001 Source: WOCG Guide, December

12 Newsprint surface microscopy Enlargement factor: 300 Enlargement factor:

13 Newsprint surface microscopy Enlargement factor: 3000 Enlargement factor:

14 Paper/ink combination (extra ink in %) LWC 1 LWC 2 LWC 3 LWC 4 LWC 5 SC 1 SC 2 SC 3 SC 4 SC 5 INP 1 INP 2 INP 3 SNP 1 SNP 2 SNP How to avoid surprises, Web Offset Champion Group, , Source: How to avoid surprises, Web Offset Champion Group,

15 Coldset is a special print process Newsink never really dryes Newsprint is porous and allows penetration Some ink penetrates into the paper Colours are de-saturated Contrast is limited 15

16 Why coldest for newspaper printing? Coldset eliminates the need for drying Speeds-up the process Simplifies the process Saves investment, space, paper cost and energy Reduces waste 16

17 Why is coldset the dominating print process for newspaper production? Short production window Night production Simple process Straight forward process Cost-efficient process Cheapest inks Cheapest paper Not drying cost 17

18 100 Why coldest for newspaper printing? 80 Coldset replaces drying by penetration 60 The downside of this simplified process includes Lower saturation and contrast 40 Newsprint Smaller colour gamut Lower resolution 20 Gloss-coated, wood-free Excessive dot gain Lower sharpness 0 Lightness Range 18

19 WAN-IFRA Special Report 2.39 Relationship between density and colour coordinates of primary colours How much can density vary within the framework of the specified colours? 19

20 Ink penetration Magenta Cyan Black Yellow Source: WAN-IFRA Special Report 2.39, 2004, P. 8 20

21 Ink penetration Magenta + Black Cyan + Black Blue Yellow + Black Red Green Source: WAN-IFRA Special Report 2.39, 2004, P. 8 21

22 WAN-IFRA Special Report Andy Williams refers to: Nurmi, Sivonen, VTT ICC profiles for different paper categories the effect of time and print through in the gamut in newspaper processes IARIGAI Conf

23 Source: WAN-IFRA Special Report , P

24 Sample from an Indian newspaper printer Blue Red Magenta Cyan Green Yellow Black Source: A. Williams, A. Srinivasan,

25 Ink penetration study Anand Srinivasan WAN-IFRA Chennai 25

26 Ink penetration study Ink dry back Effect on colour gamut 26

27 Ink penetration study Different paper/ ink combinations lead to different colour gamuts 27

28 Change in density over time Reduction of density over time of ink 1 on paper 1 Status E density, polarisation filter 28

29 Colour gamut volume reduction v. time ,03 hours , hours Time / Hours Source: A. Williams, WAN-IFRA,

30 Colour gamut 2 minutes after printing 30

31 Colour gamut 4 hours after printing 31

32 Colour gamut 4 hours after printing (white) 32

33 Ink dry-back in coldset Colour gamut may shrink up to 15% through dry-back Effects are mainly desaturation and loss of contrast Biggest change in the first half hour after printing Almost no change after four hours any more Magenta and Cyan dry back most, yellow and black less Colour difference for two-colour overprints can be between 4 or even 6 ΔEab 33

34 Ink dry-back in coldset Ink/paper combination is critical If certain colour inks dry-back differently colour shifts may happen 34

35 Before extreme Cyan dry-back 35

36 After extreme Cyan dry-back 36

37 Colour shift after dry-back 37

38 Ink dry-back in coldset Ink/paper combination is critical Test your paper and inks 38

39 39

40 Ink dry-back in coldset Pressmen measure density on wet copy Reader receives the copy after four hours Pressmen never see the colours that the readers see Find out which wet measured densities lead to which colour result (after 4 hours) What does it mean for soft proofing? Do we need special proofing profiles for wet ink? 40

41 b* Web Offset Colour Spaces Coldset, ISO Semi-Commercial, Newsprint Semi-Commercial, SC Paper Commercial Offset, ISO a*

42 Don t expect the absolute maximum! Expect the maximum possible for your process Do not try to print better than the standard! Print better with the help of the standard! If a higher quality level is required invest into the appropriate systems Follow the road from coldset to semi-commercial, to heatset drying or UV curing Hybrid systems are possible, but deliver hybrid results 42

43 What defines colour printing quality? Basic production process parameters define the possible colour quality Neutrality Lightness Contrast Details Sharpness Image resolution Number of colours Colour saturation Colour gamut Absence of defects 43

44 The colour quality value chain Different production steps influence the final print colour quality Photo shooting Ad design Colour processing Page make-up Data transmission RIP process Plate making Printing 44

45 Manfred Werfel Deputy CEO Executive Director Newspaper Production WAN-IFRA GmbH & Co. KG