Colour gamut reduction over time in a coldset process€¦ · Paper/ink combination (extra ink in...

© 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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Paper is made from natural ressources

Source: ISO Focus, February 2009

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Ink on paper – isn’t it simple like that?

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Thickness of ink film on paper

Ink film, 1 µm

Paper, 70+ µm

© 2011 WAN-IFRA

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

© 2011 WAN-IFRA

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

© 2011 WAN-IFRA

LWC = Light Weight Coated

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© 2011 WAN-IFRA

LWC = Light Weight Coated

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Ink filmInk penetration

Coating

Hole

Ink filmInk penetration

Coating

Hole


© 2011 WAN-IFRA

SC = Super Calendered

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Ink

Paper

© 2011 WAN-IFRA

NP = Newsprint

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Ink

Paper

© 2011 WAN-IFRA

Newsprint surface microscopy

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Enlargement factor: 300


© 2011 WAN-IFRA

Newsprint surface microscopy

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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

© 2011 WAN-IFRA

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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© 2011 WAN-IFRA

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

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Ink penetration studyAnand SrinivasanWAN-IFRA Chennai

Ink dry back

Effect on colour gamut

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Ink penetration study

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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Colour gamut 2 minutes after printing

© 2011 WAN-IFRA

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/paper combination is critical

If certain colour inks dry-back differently colour shifts may happen

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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

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-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

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-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

© 2011 WAN-IFRA

Manfred WerfelDeputy CEOExecutive Director Newspaper ProductionWAN-IFRA GmbH & Co. KG

[email protected]

Colour gamut reduction over time in a coldset process€¦ · Paper/ink combination (extra ink in...

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