Post on 12-Jul-2020
© 2011 WAN-IFRA
Colour gamut reduction over time in a coldset processWhat are its implications?
Manfred WerfelDeputy CEOExecutive Director Newspaper ProductionWAN-IFRA GmbH & Co. KG
© 2011 WAN-IFRA
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
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Ink on paper – not so simple at all
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WOCG Guide, December 2001
Ink film, 1 µm
Coating
Paper, 70+ µm
Source: WOCG Guide, December 2001
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How much ink on a newspaper copy?
How much ink do need to print:
One newspaper copy
48 pages broadsheet
Full colour, 4c
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5 g0,104166666666667 g per page
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LWC = Light Weight Coated
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WOCG Guide, December 2001
Source: WOCG Guide, December 2001
© 2011 WAN-IFRA
LWC = Light Weight Coated
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WOCG Guide, December 2001
Ink filmInk penetration
Coating
Hole
Ink filmInk penetration
Coating
Hole
Source: WOCG Guide, December 2001
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SC = Super Calendered
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WOCG Guide, December 2001
Source: WOCG Guide, December 2001
Ink
Paper
© 2011 WAN-IFRA
NP = Newsprint
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WOCG Guide, December 2001
Source: WOCG Guide, December 2001
Ink
Paper
© 2011 WAN-IFRA 14
How to avoid surprises, Web Offset Champion Group, 2001
Paper/ink combination (extra ink in %)
0
20
40
60
80
100
120
0,5 58
13
27
34
45
52
63
72
9598
101 100 101 103
LWC 1LWC 2LWC 3LWC 4LWC 5SC 1SC 2SC 3SC 4SC 5INP 1INP 2INP 3SNP 1SNP 2SNP 3
Source: How to avoid surprises, Web Offset Champion Group, 2001
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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
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Why coldest for newspaper printing?
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Coldset eliminates the need for drying
Speeds-up the process
Simplifies the process
Saves investment, space, paper cost and energy
Reduces waste
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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
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Why coldest for newspaper printing?
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Coldset replaces “drying” by “penetration”
The downside of this simplified process includes
Lower saturation and contrast
Smaller colour gamut
Lower resolution
Excessive dot gain
Lower sharpness0
20
40
60
80
100
Lightness Range
Gloss-coated, wood-free
Newsprint
© 2011 WAN-IFRA
WAN-IFRA Special Report 2.39
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Relationship between density and colour coordinates of primary colours
How much can density vary within the framework of the specified colours?
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Ink penetration
Source: WAN-IFRA Special Report 2.39, 2004, P. 8
Magenta
CyanBlackYellow
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Ink penetration
Blue
RedGreen
Cyan + Black
Magenta + Black
Yellow + Black
Source: WAN-IFRA Special Report 2.39, 2004, P. 8
© 2011 WAN-IFRA
WAN-IFRA Special Report 02.2007
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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. 2001
© 2011 WAN-IFRA 24
Sample from an Indian newspaper printer
Source: A. Williams, A. Srinivasan, 2009
Blue
RedMagenta
Cyan
Green
Yellow
Black
Different paper/ink combinations lead to different colour gamuts
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Ink penetrationstudy
Reduction of density over time of ink 1 on paper 1
Status E density, polarisation filter
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Change in density over time
© 2011 WAN-IFRA 29Source: A. Williams, WAN-IFRA, 2010
130000
135000
140000
145000
150000
155000
160000
0 10 20 30 40 50 60
Colour gamut volume reduction v. time
Time / Hours
0,03 hours
0,5
1
48 12 20 24 36 53 hours
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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
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Ink dry-back in coldset
Ink/paper combination is critical
If certain colour inks dry-back differently colour shifts may happen
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© 2011 WAN-IFRA
Ink dry-back in coldset
Ink/paper combination is critical
Test your paper and inks
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© 2011 WAN-IFRA
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?
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Web Offset Colour Spaces
-60
-40
-20
0
20
40
60
80
100
-80 -60 -40 -20 0 20 40 60 80
a*
b*
Coldset, ISO 121647-3Semi-Commercial, NewsprintSemi-Commercial, SC PaperCommercial Offset, ISO 12647-2
Web Offset Colour Spaces
-60
-40
-20
0
20
40
60
80
100
-80 -60 -40 -20 0 20 40 60 80
a*
b*
Coldset, ISO 121647-3Semi-Commercial, NewsprintSemi-Commercial, SC PaperCommercial Offset, ISO 12647-2
© 2011 WAN-IFRA
Don’t expect the absolute maximum!
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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
© 2011 WAN-IFRA
What defines colour printing quality?
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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
© 2011 WAN-IFRA
The colour quality value chain
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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