Colour Printing 7.0

Next Generation Multi-Channel Printing

Ludovic G. Coppel, Aditya Sole, Jon-Yngve Hardeberg

22nd Color Imaging Conference, BostonNovember 7th 2014Workshop on Next Generation Colour Printing

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Multichannel / Spectral Printing

Multilayer Printing

Colour Printing 7.0

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Next Generation Multi-Channel Printing

EU Marie Skłodowska-Curie ITN 2012 – 2015

Train a new generation of printing scientists

Research focused on multichannel and multilayer printing

7 Phd students, 2 postdocs

The project

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Spectral reproduction workflow and multi-channel printers

Halftoning for multi-channel printers

Spectral printer models, paper-ink interaction

2.5D printing, multilayering, gloss control and fine art applications

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Spectral printing

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Good spectral match colorimetric match under various viewing conditions

Spectral proofing

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Slavuj, Marijanovic, Hardeberg, “Colour and spectralsimulation of textile samples onto paper: a feasibility study,” . J. AIC 12 (2014).

Coppel, Le Moan et al., “Next generation printing - towards spectral proofing,” IARIGAI 2014.

Paramer mismatch spectral gamut mapping

Urban P. and Berns R. S. (2011), “Paramer Mismatch-Based Spectral

Gamut Mapping,” IEEE Transactions on Image Processing 20(6), 1599-

1610.

Determine all metamers in e.g. D50

Select those that are metamers in e.g. A

…

CMYKRGB space

CMYK

10400 450 500 550 600 650 700

0

0.2

0.4

0.6

Wavelength (nm)

R

C10M47Y51K28

C23M52Y56K7

Munsell 5R 6/6

E = 0.5E = 0.7metamers

E = 2.8E = 4.0 not metamers

CMYKRGB

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400 450 500 550 600 650 7000

0.2

0.4

0.6

Wavelength (nm)

R

Munsell 5R 6/6

Y23K52R56B7

E = 0.6

E = 0.5

Results: colorimetric (D50)

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ΔE2000 < 1

(%)

1 < ΔE2000 < 3

(%)

ΔE2000 > 3

(%)

CMYK 95 4 1

CMYKRGB 99 1 0

RGB channels increase the colorimetric gamut (D50)

Results: multi-illuminants

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mean

ΔE

max

ΔE

DE ≤ 1

%

DE ≤ 3

%

DE > 6

%

A CMYK col

CMYK spec

CMYKRGB

4.7

2.4

0.5

8

3.9

2.2

0

0

85

10

82

15

15

0

0

F11 CMYK col

CMYK spec

CMYKRGB

3.7

1.9

1.7

8.6

5.9

5.9

4

22

32

38

60

54

15

0

0

Spectral prints: MetaCow

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Banding artefacts

15Samadzadegan Urban, “Spatially resolved joint spectralgamut mapping and separation,” IS&T CIC (2013).

Spatially Resolved Joint Spectral Gamut Mapping and Separation

Smoother spectral separation

Preserve image edges

Model calibration

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CMYK, CMYR, CMRG, etc….

35 x 54 = 21875 calibration patches for 4-cells cellular YN modified Neugebauer model!

Model depends on:

Inks Printer Substrate Halftoning

…and needs calibration

CMYKRGB

Needs better (modular) models requiring less calibration.

Spectral colour prediction models

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Coppel, “Dot gain analysis from probabilistic spectral modelling of colour halftone,” IARIGAI (2014).

Need physical model to separate mechanical from optical dot gain Probabilistic modelling rather than Yule-Nielsen

Model fluorescence

R()

Microscale imaging

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Namedanian, Nyström, et al., “Physical and optical dot gain: characterization and relation to dot shape and paper properties,” SPIE EI Vol. 9015 (2014).

Rahaman, Norberg, Edström, “Microscalehalftone color image analysis: perspective of spectral color prediction modeling,” SPIE EI Vol. 9015 (2014).

coated uncoated

Multi-pass prints

21Olen, Padfield, Parraman, “Reproducing the old masters: applying colour mixing and painting methodologies to inkjet printing,” SPIE EI Vol. 9015 (2014).

Maximise colour saturation

Special effects (bronzing)

Subtle colour variations in darker regions

Thomas Gainsborough, Isabella (1769)

Multi-pass prints

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Colour depends on the printing order

Olen, Parraman, “Exploration of alternative print methodology for colour printing through the multi-layering of ink,” AIC (2013).

2.5D prints (lenticular)

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Ghosting reduction

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T. Baar,M. Shahpaski, andM. V. Ortiz Segovia, “Image ghosting reduction in lenticular relief prints,” in Proc. SPIE Vol. 9018 (2014).

Compensates for cross-talk (ghosting) making parts of one image remaining visible in the viewing direction corresponding to the other image.

Printing gloss effects

25T. Baar, S. Samadzadegan, H. Brettel, P. Urban, and M. V. OrtizSegovia, “Printing gloss effects in a 2.5D system,” in “Proc. SPIEVol. 9018,” (2014), pp. 90180M–90180M–8

Gloss control

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Standard prints: gloss increases with ink coverage.2.5 D printing allows printing nearly constant gloss value independently of ink coverage.

Print on white layer increases gloss

Multi-pass printing increases roughness

Gloss can be controlled by time between white layers

Time dependent gloss

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Measured gloss as a function of

time delay between two white

layers in WWCMY print mode.

Multiple ICC profiles

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T. Baar and M. Segovia, “Colour management of prints with variantgloss,” in IS&T 22nd Color and Imaging Conference (2014).

Assessing Quality

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How to evaluate the outcome of 2.5D prints?

What about spectral images?

Gloss perception

Baar, Brettel, Segovia, “A survey of 3d image qualitymetrics for relief print evaluation Metrics” CVCS Gjøvik (2013).

Spectral image difference

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original repro Lightness structure difference

Hue difference map

Le Moan, Urban, “Image-difference prediction: From colorto spectral,” IEEE Transactions on Image Processing (2014).

Spectral Profile Connection Space

32Le Moan, Urban, “A new connection space for low dimensional spectral color management”, SPIE Electronic imaging Vol. 9018 (2014).

Conclusions

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Multi-channel and multi-layering (2.5D/3D) printing open new research areas and applications in printing.

CP7.0 outcomes:o Significant contributions to spectral printing workflowo Deeper understanding of light-paper-ink interactiono 2.5D printingo Method for controlling glosso Fine art reproductiono Framework for spectral image quality assessment and

communication of spectral images

CP7.0 outlook

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What future for printing spectral?

How many colour channels do we need?

Reproducing material appearance

What market?

Thank you!

Ludovic.coppel@hig.nowww.colourlab.nowww.cp70.org

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