The Spectral Printer: From Technical Challenge To Business Case

© Copyright 2013 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.

THE SPECTRAL PRINTER: FROM TECHNICAL CHALLENGE TO BUSINESS CASE

Dr. Ján MorovičSenior Color Scientist / Master Technologist, Hewlett–Packard CompanyDirector of CIE Division 8: Image Technology

8th ROND Conference, 14th March 2013, Örnsköldsvik, Swedenhttp://fotonerdz.deviantart.com/art/Matrix-spectrum-278731679

http://fotonerdz.deviantart.com/art/Matrix-spectrum-278731679

http://fotonerdz.deviantart.com/art/Matrix-spectrum-278731679


Can we make it?

Can we make moneyfrom it?

WHICH COMES FIRST?


OUTLINE

• What is spectral printing? (Again!)

• Can we make it?

• Technology: inks, substrates, gamut, separation, workflow, content

• Customer benefit: “Will I see it?”

• Can we make money from it?

• Market size: how many billion pages/$?

• Added value: premium pricing / new applications?

• Conclusions


WHAT IS SPECTRAL PRINTING?

Match original under any light source.Match for all observers (human, animal).→ Reproduction changes with illumination like the original does and for all viewers.

‘I can see what the Mona Lisa would look like in my living room’

BUT: “Match” is aim, not necessarily property!

Light sourceLight source

Light source 1

O P

Light source 2

O P


SO, WHAT IS COLOR PRINTING?

Designed to match color under one light source (D50) and for human observers with certain cone sensitivities.

BUT: • ∆Es even under chosen light source• Uncontrolled/unknown ∆Es under other light sources

Assumption: for a spectral print, color differences under variety of light sources are lower than for colorimetric (metameric) print.

Light sourceLight source

Light source 1

O P

Light source 2

OPP?


ANY OTHER ‘SPECTRAL’?

• Focus here on spectral printing (i.e., aiming at a match of spectral reflectance between original and reproduction).

• Spectral data also has benefits for metameric reproduction• Metameric match under non-standard / multiple

light sources• Modeling of colorant interactions (e.g. spot color

overprinting)• Modeling of printer behavior


HOW DO I MAKE A SPECTRAL PRINT?

Matching

Halftoning Colorants Substrate

Spectral content

Gamut mapping


WHERE CAN I GET SPECTRAL CONTENT?

• Spectral image capture → broadly applicable, but still scarce

• Spectral measurement → applicable to color palettes (e.g., Pantone)

• Predicted from original device’s model → when original is a print, spectra can be predicted using model of it’s colorants and halftoning

• Predicted from colorimetry / trichromatic capture → colorimetric capture + measurements to characterize spectral basis (e.g., of artwork)

• Without spectral content, spectral printing is inapplicable → not going to replace metameric color reproduction wholesale

Spectral content Gamut mapping Matching Halftoning Colorants Substrate


HOW DO I ADAPT IT TO MY MATERIALS?

• Single-shot mapping

• Direct spectrum → colorant amounts mapping (optimization/regression, computationally expensive, disregards visual system entirely) (e.g., Bastani et al., 2006)

• Gamut mapping + Matching

• Color gamut mapping to gamut of 3 fundamental bases + spectral mapping in metameric blacks (Chau and Cowan, 1996)

• Sequential color mapping: match under illuminant U, then to V in remaining metamer set, then to W, etc. (Urban et al., 2008)

• Workflow considerations

• LabPQR (Derhak and Rosen, 2004) → extension of ICC framework, easy WF integration

• Result: spectrum to colorant amounts



TWO-STAGE MAPPING & LABPQR


HOW DO I BUILD COLORANT PATTERNS?

• Challenges:

• Multiple colorants (CMYK+)

• Difficulty of applying threshold matrix halftoning (AM/FM) → moire

• Potentially abrupt changes in colorant space → artifacts

• Solutions:

• Error diffusion (Norberg, 2012)

• BUT: “arbitrary” multi-colorant patterns challenging



AN ALTERNATIVE: HANSSpectral content Gamut mapping Matching Halftoning Colorants Substrate

tesserae/ tiles!

Neugebauer Primaries (NPs) / at-pixel ink drop states!

artist!

mosaic! pr

int!

printer (inks, media, WS, FW, pipeline)!

Printing as mosaic assembly

Separation: colorant amount selection → Neugebauer Primary

(NP) statistics

Halftoning: per colorant continuous levels to discrete drops → NP per

pixel from local statistics



gamut mapping

reflectance reflectance

colorantmatching

colorant vector

colorant space

halftoning

drops / pixel /

colorant

NPmatching

NP area coverage

vector

NP space halftoning

colo

rant

w

orkfl

owH

ANS

wor

kflow



• The reflectance of a pattern is the convex, area-coverage-weighted combination of it’s NPs’ reflectances (corrected for dot gain) → YNSN

• A reflectance can be matched if there exists a simplex in reflectance space, that has the reflectances of a printing system’s NPs as its vertices

• The area coverages that need to be assigned to each NP match the convex weights with which it needs to be combined to match the target spectrum

• Operating in NP space offers vastly more choice: n versus kn dimensions (for n colorants and k levels per colorant per pixel)

• E.g., for 6-ink printer with up to 3 drops per ink per pixel, HANS has 46=4096D versus the 6D of a colorant workflow

• The rest is brute (or not so brute) force!

Alternative basic NPacs:!

6086!(in 34=81D)!

Alternative basic ink combinations:!2!(in 4D)!

C=34%!M=27%!Y=28%!

C=7%!Y=1%!K=27%!

W=77%!C1=1%!Y1=2%!K1=20%!

W=79%!Y1=2%!K1=14%!Y1K1=2%!C2=1%!K2=2%!

W=70%!C1=2%!M1=5%!Y1=5%!K1=6%!C1M1=1%!C1K1=2%!M1K1=3%!Y1K1=2%!C2=4%!

Print color!

3000x possible

patterns (same color)!

included!



• HANS error diffusion:

• Error is computed in area coverage terms

• Area coverages account for optically-additive aspect of print color formation

• Arbitrary NP combinations can be formed and transitioned between

• Non-linearity of colorant interactions is handled prior to halftoning, which can then operate in an additive space


COLORANTS AND SUBSTRATE

• What colorants are best for spectral reproduction?

• Several studies (e.g., Tzeng, 1999)

• Narrow-band, inverted Gaussians (from first principles; Chen, 2004)

• BUT, constraints from:

• what is physically realizable

• what can be manufactured in bulk

• what can be successfully jetted or deposited using other marking engines

• Substrate’s colorant limit (rules out Gaussians)



COLORANTS AND SUBSTRATESpectral content Gamut mapping Matching Halftoning Colorants Substrate


WILL MY CUSTOMERS SEE THE DIFFERENCE?


WHAT MAKES A GOOD SPECTRAL PRINT?

• Many metrics defined in the literature

• Purely spectral, taking into account CMFs, focusing on metamerism between specific light sources, looking at sets of color difference statistics per light source + combinations of these

• BUT: how does an observer experience the goodness of a spectral match?

• Original – print ← observer

• Observer views original-print-pair under many light sources (not arbitrary → database of measured lights)

• Under each light source they see certain levels of color difference (→ most accurately predicted by ∆E2000, with JND units)

• Surveying their experiences from under multiple light sources gives rise to a variety of color difference magnitudes (→ choice of relevant statistics)


MIPE: AN EXPERIENCE–BASED METRIC

20

Paramers (>0 ∆E even under

‘reference’ illuminant)

Non-parametric descriptive statisticsMedian: how close a match can be

expected for an arbitrary, but realistic, light source

95th percentile – median: how much this match varies

Maximum: how far apart the two can get at worst

Light sources / illuminantsCIE standard and recommended illuminants

+ measured light sources

Color differencewith visually meaningful

units (~JND)


SPECTRAL ‘GOODNESS’ OF METAMERIC PRINT

Colorimetric ‘goodness’ Spectral ‘goodness’

matte glossy

HP Designjet Z310010 inks: cMmYnNKRGB + glossy/matte black + gloss enhancer

Spot color: PANTONE uncoated, matte and coated, 1224 patches per substrate (3672 total samples; mixtures of Pantone system’s 15 base inks)Fine art: 1168 measurements taken from paintings

• Similar performance under D50 (for which colorimetry was matched) and all other 172 illuminants (color gamut differences a big contributor already)

• MIPE errors higher than D50 ∆Es (sanity check for maximum)

• → Gap between MIPE and D50 ∆Es indicates room for improvement from spectral matching


SPECTRAL ‘GOODNESS’ OF SPECTRAL PRINT


TECHNICAL CHALLENGES

• Degree of “spectral goodness” benefit versus metameric reproduction

• spectral workflow + inherent limits of materials used

• more colorants ≠ better spectral performance (necessary but not sufficient)

• Way forward:

• Dedicated spectral reproduction colorants

• Efficient spectral workflow

• Experience-focused optimization

• Availability of content


STANDARDS? (A.K.A. THE CIE SALES PITCH)

• CIE Technical Committee 8-07 Multispectral Imaging (chair: Masahiro Yamaguchi)

• Terms of reference: To study, develop and recommend encoding techniques and data formats for the exchange of multispectral images, and to provide test procedures for the evaluation of multispectral imaging systems.

• Technical report due end ’13: will provide basics of multispectral format requirements & compare four alternative formats


CAN I MAKE MONEY FROM IT?


ADDRESSABLE MARKET ($846B IN 2016 WW)

1%2%3%4%4%

5%

8%

13%

18%

43%

Packaging Commercial Advertising Magazines NewspapersBooks Catalogues Office Directories Security

14%

86%

Potentiallyspectral

Non-spectral

$364B

Source: PIRA

$118B

http://www.slideshare.net/adampage1976/global-print-markets-to-2016

http://www.slideshare.net/adampage1976/global-print-markets-to-2016


SPECTRAL APPLICATIONSApplication Feasibility Salability

Proofinghigher (content available, matching has good chances ← similar materials)

higher (similarity to production print is essence of proof → spectral is clearly

better than metameric proof)

Fine-art reproduction medium (content availability limited, material differences greater)

medium (spectral match to original may not always be desired → Mona Lisa in Louvre v. my

kitchen)

Catalogues lower (content scarce, materials potentially very different)

higher (color differences are source of many returned good, better reproduction → more

profitable operation)

Security higher (spectral differences are created among available metamer sets, not v. original)

higher (persistent need for ever broadening variety of features; closer ties to original materials if spectral properties exploited)


WHERE DOES THE MONEY COME FROM?

• “Better” reproduction → proof, fine art print

• New features → security

• Secondary benefits → reduction lost profit from returned goods (catalogues)

• Premium pricing v. differentiation from competitors (print as commodity)


A TALE OF TWO PRINTERS

• Printer A: the hunting knife

• Dedicated spectral printing colorants & printing technology + spectral workflow• + Excels at spectral printing; limited addressable market• - Not suitable for ‘color’ printing (ink use, grain, cost)

• Printer B: the Swiss Army knife

• General purpose materials & technology (+ spectral workflow)• + Suitable for spectral or ‘color’ printing; large addressable market• - Less spectrally accurate than Printer A


CONCLUSIONS

• There are multiple applications that can benefit from spectral printing

• Colorants developed specifically for spectral printing would boost its potential

• Solutions need to focus on customer/viewer experience


ACKNOWLEDGEMENTS

• Peter Morovič

• Juan Manuel García-Reyero

• Martí Rius

• Jordi Arnabat

• Johan Lammens

• Carlos Amselem

• Ole Norberg


THANK YOU!

The Spectral Printer: From Technical Challenge To Business Case ￼

Technology

Transcript of The Spectral Printer: From Technical Challenge To Business Case ￼

The Spectral Printer: From Technical Challenge To Business Case

Transcript of The Spectral Printer: From Technical Challenge To Business Case