This document summarizes the research from the Colour Printing 7.0 project focused on next generation multi-channel and multi-layer printing. The project involved 7 PhD students and 2 postdocs researching topics like spectral reproduction workflows, halftoning for multi-channel printers, and 2.5D/multilayer printing. Key outcomes included contributions to spectral printing, understanding light-paper-ink interaction, methods for controlling gloss in 2.5D printing, and frameworks for assessing spectral images. The project provided insights into research areas opened by multi-channel and multi-layer printing technologies.

1. Colour Printing 7.0
Next Generation Multi-
Channel Printing
Ludovic G. Coppel, Aditya Sole, Jon-Yngve Hardeberg
22nd Color Imaging Conference, Boston
November 7th 2014
Workshop on Next Generation Colour Printing

2. 2
 Multichannel / Spectral Printing
 Multilayer Printing

3. Colour Printing 7.0
3
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

4. The project
 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
11/11/2014 4

5. 6

6. Spectral printing
7
Good spectral match  colorimetric match under
various viewing conditions

7. Spectral proofing
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Coppel, Le Moan et al., “Next generation printing - towards spectral
proofing,” IARIGAI 2014.
Slavuj, Marijanovic, Hardeberg, “Colour and spectral
simulation of textile samples onto paper: a feasibility study,” . J. AIC
12 (2014).

8. 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

9. CMYK
10
0.6
0.4
0.2
0
400 450 500 550 600 650 700
Wavelength (nm)
R
C10M47Y51K28
C23M52Y56K7
Munsell 5R 6/6
E = 0.5
E = 0.7
 metamers
E = 2.8
E = 4.0
 not metamers

10. CMYKRGB
11
0.6
0.4
0.2
0
Y23K52R56B7
400 450 500 550 600 650 700
Wavelength (nm)
R
Munsell 5R 6/6
E = 0.6
E = 0.5

11. Results: colorimetric (D50)
ΔE2000 < 1
(%)
1 < ΔE2000 < 3
(%)
ΔE2000 > 3
(%)
CMYK 95 4 1
CMYKRGB 99 1 0
 RGB channels increase the colorimetric gamut (D50)
11/11/2014 12

12. Results: multi-illuminants
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
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13. Spectral prints: MetaCow
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14. Banding artefacts
15
Samadzadegan Urban, “Spatially resolved joint spectral
gamut mapping and separation,” IS&T CIC (2013).
Spatially Resolved Joint Spectral
Gamut Mapping and Separation
 Smoother spectral separation
 Preserve image edges

15. Model calibration
16
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.

16. Spectral colour prediction models
18
 Need physical model to
separate mechanical from
optical dot gain
 Probabilistic modelling
rather than Yule-Nielsen
 Model fluorescence
Coppel, “Dot gain analysis from probabilistic spectral
modelling of colour halftone,” IARIGAI (2014).
R()

17. Microscale imaging
19
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, “Microscale
halftone color image analysis: perspective of spectral
color prediction modeling,” SPIE EI Vol. 9015 (2014).
coated uncoated

18. Multi-pass prints
 Subtle colour variations in darker regions
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 Maximise colour saturation
 Special effects (bronzing)
Olen, Padfield, Parraman, “Reproducing the old masters: applying colour mixing
and painting methodologies to inkjet printing,” SPIE EI Vol. 9015 (2014).
Thomas Gainsborough, Isabella (1769)

19. Multi-pass prints
22
Colour depends on the
printing order
Olen, Parraman, “Exploration of alternative print methodology for
colour printing through the multi-layering of ink,” AIC (2013).

20. 2.5D prints (lenticular)
23

21. Ghosting reduction
Compensates for cross-talk (ghosting)
making parts of one image remaining visible
in the viewing direction corresponding to
the other image.
24
T. Baar,M. Shahpaski, andM. V. Ortiz Segovia, “Image ghosting
reduction in lenticular relief prints,” in Proc. SPIE Vol. 9018 (2014).

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

23. Gloss control
26
 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

24. Time dependent gloss
Measured gloss as a function of
time delay between two white
layers in WWCMY print mode.
27

25. Multiple ICC profiles
28
T. Baar and M. Segovia, “Colour management of prints with variant
gloss,” in IS&T 22nd Color and Imaging Conference (2014).

26. Assessing Quality
29
 How to evaluate the outcome of 2.5D prints?
 What about spectral images?
 Gloss perception
Baar, Brettel, Segovia, “A survey of 3d image quality
metrics for relief print evaluation Metrics” CVCS Gjøvik (2013).

27. Spectral image difference
31
original repro Lightness structure
difference
Hue difference map
Le Moan, Urban, “Image-difference prediction: From color
to spectral,” IEEE Transactions on Image Processing (2014).

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

29. Conclusions
33
 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 workflow
o Deeper understanding of light-paper-ink interaction
o 2.5D printing
o Method for controlling gloss
o Fine art reproduction
o Framework for spectral image quality assessment and
communication of spectral images

30. CP7.0 outlook
34
 What future for printing spectral?
 How many colour channels do we need?
 Reproducing material appearance
 What market?

31. Thank you!
Ludovic.coppel@hig.no
www.colourlab.no
www.cp70.org
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