Printing the Expected

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Andreas Kraushaar | kraushaar@fogra.org 1

Printing the

Expected

The IGF research project Fogra No. 35.003 of the Fogra Graphic Technology Research Association, Streitfeldstrasse 19, 81673 Munich, was funded by the AiF under the program for promoting industrial research and development(IGF) of the Federal Ministry of Economics and Technology, based on a resolution of the German Bundestag.

Consistent colour rendering across all media

Internet

¬ Typical colour gamuts

¬ Representing the range of output media

¬ Act as an interchange or exchange space

„Multi Channel Publishing“

Printing

Tablet PC DVD, Motion

Picture

Conventional Printing Digital Printing

PIA Color Management Conference, 2011

Agenda

1. Who and what is Fogra?

2. How about customer expectations?

3. Image appraisal types (for digital printing)

4. From ISO 12647-2 ISO 15311

5. The challenges for image quality assessment

6. Image quality attributes in details

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Andreas Kraushaar | kraushaar@fogra.org

1. The industry needs independent research

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In 1951 the german printing industry (small and medium enterprises) decided to put some money together

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Fogra stands for “Forschung im grafischen Gewerbe” - research in the graphic arts

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Fogra is “governed/owned” by its members (who also constitute the board of directors) neutrality

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Aiming for an “lawyer of the printer” - an manufacturer independent organization

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Similar organizations in US (GATF), UK (PIRA), Switzerland (Ugra), Spain (AIDO), etc

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Fogra is financed (ca. 5 Million € turnover) by ¬ 1 Mio. membership fees

¬ 2 Mio. research funds from the country/state/EU (based on extensive application)

¬ In order to compensate for the remaining losses, Fogra provides regular services such as control wedges, certifications, symposia etc

4

Research And development

Fogra-Services

1. Fogra - the service provider in the

graphic arts industry

Fogra, active in four fields of activities

Consultancy

, measuring and expert opinions

Committee work and

Standardization Dissemination _and

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2. What are the customer's expectations?

5

Consistent colour rendering across all media

Internet

Printing

Picture

ISO 15930-7: to permit the predictable dissemination of a compound entity to one or more

locations.

Lets ask PDF/X

Full Reference

Are there more expectations?

Sure!

2. Zero and Full reference

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Consistency

¬

Predictability

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Closer is better Accuracy

Zero Reference

¬

Make it "Sexy" Match Preferences

Do we need to have the same

level of accuracy (tolerances)?

Certainly not.

ISO 15311 proposal: Quality types A, B & C

(4)

3. Digital Printing - Types of image appraisal

achieving the same colour on totally different substrates Being able to reproduce the same colour to replace a part or reprint after a while

Being able to print without visible banding (uniform). Resolution is depending on distance and size

7

Source: R. Blind

¬ Proofing [ISO 12647-7] ¬ Validation Print [-8]

¬ PSO ISO 12647-2

¬ PSD ISO 15311-x

Side-by-Side

5. ISO 15311 provides 3 levels of predictability

Predictability of the final colour - upfront

¬ PSD ISO 15311-x

¬ “Common

Appearance”

¬ big gamut differences Side-by-Side

consistent colours

Partial Colour Ref.

¬ PSD ISO 15311-x

¬ small gamut-difference between ref. and print Comparison w. memory

media-relative colours

Full Colour Ref - Media Relative

Identical colours

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4. From ISO 12647-2 to ISO 15311-1

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Complex but mostly known behavior of components and their

interplay separable standardizeable

Offset

Ink Machine Paper wet in wet

Highly integrated systems. Hardly separable

Define Combinations Define expected outcome

Digital

Ink Machine Substrates different technologies

4. ISO 15311-1: The toolbox for image quality

Graphic technology - Requirements for printed matter utilizing digital printing technologies for the commercial and industrial production - Part 1: Parameters and measurement methods

Scope

This part of ISO 15311 defines print quality attributes and

measurement methods for digital prints. These parameters

provide a basis to allow subsequent parts of this International

Standard to define acceptable conformance criteria for

particular use cases.

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4. Laboratory and Practical criteria

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4.3.2 Colour and surface finish

4.3.2.1 Requirements of unprinted substrate 4.3.2.2 colour accuracy requirements 4.3.2.3 Consistent reproduction of tone values 4.3.2.4 Ink Set Gloss

4.3.2.5 Further criteria

4.3.3 Homogeneity

4.3.3.1 Streakiness 4.3.3.2 Background Haze 4.3.3.3 Graininess and Mottle 4.3.3.4 Fill (caries)

4.3.3.5 Inking variation across the format and within the printing direction 4.3.3.6 Further criteria 4.3.4 Resolution 4.3.4.1 Line Width 4.3.4.2 Native Addressability 4.3.4.3 Effective addressability 4.3.4.4 Raggedness 4.3.4.5 Blurriness

4.3.4.6 MTF (Modulation transfer function) 4.3.4.7 Register

4.3.4.8 Patterning 4.3.4.9 Further requirements

4.3.5 Artefacts

4.3.5.1 Contouring

4.3.5.2 Spreading (misdirected dots, satellites) 4.3.5.3 Use case specific criteria

"System Check" "Print Check"

?

dedicated criteria for systems & printer

Consistent colour rendering across all media

4. Potential implementation

ISO 15311 ISO 12647

Contract

Proof Valida9onPrint Produc9onLite LFP

....

-7

-8

Conven9onal Prin9ng Digital Produc9on

-1 -2 Oﬀsetprint -2/3 Concept, Toolbox -3

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5. Challenges for image quality assessment

13

„When you can measure what you are speaking about and express it in numbers, you know

something about it“

Lord W. T. Kelvin, Lecture to the Institution of Civil engineers, London, 3 May 1883

„The ultimate test of any colour reproduction is the opinion of the person who views it. But opinions differ...“

R. W. G. Hunt. In: The reproduction of color

We need objective measures

(if possible based on agreed upon standards)

We need to focus on use cases which provides

(full) reference (contrary to no reference)

"All colors must be evaluated numerically".

A. Kling, Keynote, Color Management Conference

1,2,3 - Scope, normative references, terms & definitions

4 - requirements 4.1 data

4.2 digital print _substrates

coloration rub resistance ink set gloss reproduction limits tone value repro vignettes resolving power margin info gamut data halftone

5 - Test methods 5.1 control strip

5.2 test objects, measurements, visual Annexes [A: metal slab | B: Certification]

5. How is print image quality define so far?

ISO 12647-7/8

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5. Categorization of image quality attributes

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Colour

reproduction

Uniformity

Resolution

Artefacts

Permanence

Functional

performance

System

¬

Productivity

¬

on site reliability

¬

etc.

Health, Safety,

Environment

arbitrary but useful

6. Image quality attributes in details

Colour

Perceptual Resolution

Homogeneity

Artefacts

concept: Individual attributes contribute to a recognized overall

image quality. (compare the rating of food)

1 2 3 4 5 6 ... Quality Type A Quality Type B

+ individual

needs

Quality Type C

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Providing tolerances for the three quality types

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Providing tolerances for spot colour reproduction ¬ based an selected image appraisal types (identical versus media-relative)

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Common appearance to be added later

6.1 Evaluation of the colour reproduction

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current candidate of ISO 15311-2

6.1 Colour: Number of visual & technical discernible

tonal steps

(10)

6.2 Perceptual resolution - concept

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Testchart-Design _{(Driving) - “RIP-resolution”}Correct Interpretation _{- “Imaging-resolution”}Printing

Print Inspection (visually | measurement wise) Resolution attributes Perceptual Resolution Correlate ¬ native addressability ¬ effective addressability ¬ edge blurriness ¬ edge raggedness ¬ MTF ¬ more to come

6.2 Perceptual resolution

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Different tolerances for the pertinent quality levels

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edge blurriness and edge raggedness

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legibility

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Mis-registration

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6.2 Correlates tested so far at Fogra

21 1 2 3 4 5 • Edge Sharpness (inverse of blurriness)

– a measure of the average edge profile transition width in the direction perpendicular to the edge

– using the square

• Edge Raggedness

– a measure of the average edge profile variation (50%) in the direction parallel to the edge

– using the rotated squares with 8 degree

JTC1, SC28 WG4 works actively on these measures ¬Further fine tuning is needed

¬Round robin tests are underway

¬Practical aspects of scanner influence, repeatability and reproducibility are yet to be evaluated

6.2 blurriness and raggedness in detail

Scan

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6.2 Mis-Registration (example)

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¬ Digital production machine ¬ Print Run: 500

¬ Data Path: Device Mode

¬ Test elements: 4 Positions

¬ Format: SRA3

2000 measurements for K/C, K/C, K/Y

printing direction Pos. 1 Pos. 2 Pos. 3 Pos. 4

A

B

C

6.3 Evaluation of homogeneity

Homogeneity (uniformity) subjective impression of colour uniformity across a large image that is intended to have a uniform colour.

Refers to all types of colour variation:

¬

lightness, hue, saturation

¬

derivatives of these can be measured separately or in combination Variation geometry:

¬

1D, 2D, periodic, aperiodic, localized, large-scale, and small-scale variation, separately or in combination such as streaks, bands, gradients, mottle, graininess and moiré.

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6.3 Evaluation of homogeneity

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Development of M-Score: 0 .. 100

1. Compute the CIELAB colour differences ∆E00 between neighbouring patches

2. Sum measurements for rows and columns and

normalize them.

3. Calculate M-Score

6.3 M-Score in detail

M-Score Meaning Comments

≥ 95 Perfect Inkjetprint on proofing substrate showing no

visible inhomogeneities

> 80 Very Good Print with slightly visible inhomogeneities (e.g.

some Mottling). No visible stripes.

> 70 Good Print with visible inhomogeneities (Mottling) but

almost no visible stripes.

> 60 Satisfactory Mottling and stripes visible. Is still accepted by

most observers.

> 50 Adequate Print with clearly visible mottling and/or stripes.

Acceptance is highly dependent on the printed image.

< 50 Poor (But

sellable)

Clearly visible mottling and stripes. Not accepted as high quality print

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based on a evaluation of photo books (toner based systems)

6.3 How to use M-Score in a standard ….

27

ISO 15311-2 candidate

toner based systems

6.3. Homogeneity: Next steps

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M-Score works good for toner based systems (i.e. it correlates well with absolute (magnitude estimation) and relative scales (rank order))

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It ought to be tested how much similar metrics such as ISO 13660 (replacement: ISO 24790) mottle improve the performance

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It will be evaluated also for inkjet prints

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6.3. Homogeneity: One word about graininess

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test charts different levels of graininess

Rank order experiment

¬ We propose three default viewing distances (50 cm [reading], 100 cm [POP] and 1,5 m [Large Format]

¬ Simple evaluation of standard test chart with a standard scanner

Why did I leave out ISO 15339?

Consistent colour rendering across all media

Internet

Printing

Picture

ISO 12647-x ISO 15311-x

(16)

¬

Think about customers expectation

¬

ISO 15311 defines new (old) things:

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Different levels of quality types (currently A, B & C)

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Different ways of image appraisal

(Sidy-by-Side and media relative)

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Framework for common appearance (to be added if

understood objectively)

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Defining capabilities of combination rather than

individual components

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A collection of important image quality attributes has

been collected and is under testing

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Setup your workflow accordingly to print the expected

Summa

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Dr. C. E. K. Mees (Kodak)

7. Together we can do it

“The best person to decide what research work shall be

done is the man who is doing the research.

The next best is the head of the department.

After that you have the field of best persons and meet

increasingly worse groups.

The first of these is the research director, who is

probably wrong more than half the time.

Then comes a committee, which is wrong most of the time.

Finally there is the committee of company vice-presidents,

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drupa 2012

33

8. If you are close to germany, come by

You got compared anyhow. Here you know the rules

and the referee!

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Andreas Kraushaar | kraushaar@fogra.org 1. Output process -control

✔

large format small format 2. Colour Fidelity 3. Workflow

✔

Consistency Match ✔ Preflight ✔ PDF/X-Creation ✔ PDF/X-Output

✔ Altona Test Suite V1 & V2

✔ Profile-handling ✔ Light-Audit

prepress

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8. The PSD-concept: An overview

RGB

CMYK

1

reference

actual print

CMYK

2 Separation Proof to Print Match e.g. FOGRA39

e.g. ECIV2 ISO 12647-2 _{PT 1/2}

Common appearance in a nutshell

RGB

CMYK

1

CMYK

2

Separation

Proof to Print Match

e.g. IFRA26

e.g. ECIV2 ISO

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Andreas Kraushaar | kraushaar@fogra.org 37

You can print “nicely” with it and you might achieve similar/identical results But it is not spot on on ISO 12647-2 TVI aims

Printing the Expected

Printing the

Consistent colour rendering across all media

Agenda

Research And development

1. Fogra - the service provider in the

Consultancy

2. What are the customer's expectations?

Consistent colour rendering across all media

Lets ask PDF/X

3. Digital Printing - Types of image appraisal

¬ PSO ISO 12647-2

5. ISO 15311 provides 3 levels of predictability

4. From ISO 12647-2 to ISO 15311-1

Scope

4. Laboratory and Practical criteria

4.3.2 Colour and surface finish

4.3.5 Artefacts

4. Potential implementation

ISO 15311 ISO 12647

5. Challenges for image quality assessment

We need objective measures

5. How is print image quality define so far?

concept: Individual attributes contribute to a recognized overall

6.2 Perceptual resolution - concept

6.2 Correlates tested so far at Fogra

6.2 blurriness and raggedness in detail

6.3 Evaluation of homogeneity

M-Score Meaning Comments

< 50 Poor (But

6.3 How to use M-Score in a standard ….

Why did I leave out ISO 15339?

Consistent colour rendering across all media

Think about customers expectation

been collected and is under testing

After that you have the field of best persons and meet

8. If you are close to germany, come by

8. The PSD-concept: An overview

Creative work