ISO/DIS 12647-9

Graphic technology -- Process control for the production of half-tone colour separations, proof and production prints

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DRAFT INTERNATIONAL STANDARD
ISO/DIS 12647-9
ISO/TC 130 Secretariat: SAC
Voting begins on: Voting terminates on:
2020-04-02 2020-06-25
Graphic technology — Process control for the production
of half-tone colour separations, proof and production
prints —
Part 9:
Metal decoration printing processes using offset
lithography
ICS: 37.100.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
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BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
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NATIONAL REGULATIONS.
ISO/DIS 12647-9:2020(E)
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NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
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ISO/DIS 12647-9:2020(E)
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ISO/DIS 12647-9:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Requirements .......................................................................................................................................................................................................... 2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Data files and printing formes ................................................................................................................................................... 2

4.2.1 Data delivery ....................................................................................................................................................................... 2

4.2.2 Printing forme quality ................................................................................................................................................. 3

4.2.3 Screen frequency (periodic screens) .............................................................................................................. 3

4.2.4 Dot size (non-periodic screens) .......................................................................................................................... 3

4.2.5 Screen angle (periodic screens) .......................................................................................................................... 3

4.2.6 Dot shape and its relationship to tone value (periodic screens) ............................................ 3

4.2.7 Tone Value Sum ................................................................................................................................................................. 3

4.2.8 Grey reproduction and grey balance .............................................................................................................. 4

4.3 Proof or production print .............................................................................................................................................................. 4

4.3.1 General...................................................................................................................................................................................... 4

4.3.2 Visual characteristics of image components - Print substrate colour ............................... 5

4.3.3 Ink set colours (colorant description) .......................................................................................................... 5

4.3.4 Tone value reproduction limits ........................................................................................................................... 6

4.3.5 Tone value increase and spread .......................................................................................................................... 6

4.3.6 Tolerance for Image Positioning ......................................................................................................................... 9

4.3.7 Conformance ....................................................................................................................................................................... 9

5 Measurement methods ...............................................................................................................................................................................10

5.1 Computation of densities, CIELAB colour coordinates and CIELAB colour differences .......10

5.2 Control strip ...........................................................................................................................................................................................10

Annex A (informative) Grey reproduction and grey balance ...................................................................................................11

Annex B (informative) Handling differences in coating colour .............................................................................................13

Bibliography .............................................................................................................................................................................................................................14

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ISO/DIS 12647-9:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 130, Graphic technology.

A list of all parts in the ISO 12647 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/DIS 12647-9:2020(E)
Introduction

ISO 12647-1 serves to provide definitions, general principles, the general order and materials to be

covered in ISO 12647-2 to ISO 12647-9, the definition of the data, the measurement conditions, and the

reporting style.

This part of ISO 12647 relates to the subject of offset printing on coated metallic substrates and

establishes the printing requirements for the metal decoration market. This market includes metal

boxes and cans in which the printing is performed directly onto the white coated surface of the metal

prior to the formation of a container.

This part of ISO 12647 specifies aim values (or sets of aim values) and tolerances, for the primary

parameters specified in ISO 12647-1 for digital proof printing. Primary parameters that define a

printing condition include screening parameters (where applicable), the colours of the solids, the colour

of the print substrate, colours of intermediate tint values and the tone curve. Adherence to these values

essentially ensures that a grey which at the colour separation stage was composed for a specified

printing condition also prints as a grey colour when both proofing and printing. Remaining deviations

from grey due to differences in trapping can then be removed by adjusting the colouration within the

tolerances provided. This part of ISO 12647 also specifies test methods for those properties of prints

and their substrates that are considered relevant for stable and reliable metal deco reproduction.

Typically, the specified printing condition is defined through an International Color Consortium

(ICC) profile or the associated characterisation data set, both of which relate the source data and the

colorimetrically defined printed colour. Such data may be derived from printing conditions conforming

to the pertinent process standard of the ISO 12647 series by industry trade groups or individuals.

Printing on metallic substrates poses some unique challenges. Sometimes, the metal surface is pre-

coated with an opaque white and then the coloured inks are printed on top of the white coating. Other

times the coloured inks are printed directly onto the metallic surface and the nature of the bare metal,

shininess, texture or polishing marks may be observed and measured through the ink layer. Most

metallic substrates are ETP (electrolytic tinplate), TFS (tin free steel) and aluminium, all coated with

a white coating or pre-printed with a printing white ink before being printed with coloured inks. This

document considers only the substrates, which are pre-coated with a white coating.

Historically, there has been no consistency in the way that either the characterisation data or the

criteria and limits for a satisfactory match have been provided. This has led to significant redundancy

and inconsistencies in the evaluation of proofing systems for different, but similar, applications, and

a cost and time burden on the industry. This International Standard therefore attempts to provide

guidance in this area by providing specifications and associated testing procedures.

Part 9 of this International Standard defines requirements for printing offset on metallic substrates

that have been pre-coated with a white coating. Bare metallic substrates have not been included

because of the complexity of the specular and surface reflection requirements. Also, the grey nature

of the substrate means that it will always be restricted in gamut and difficult to manage. The industry

does not print much process imagery on bare metal.

This document does not specifically consider the production of spot colours from a process printing

approach. However, such colours can be generated from such an approach and the tolerances should be

agreed between the buyer and the seller. Spot Colour management is defined in this document to utilize

spectral data in an .xml schema defined by ISO 17972-1, Graphic technology — Colour data exchange

format — Part 1: Relationship to CxF3 (CxF/X) and ISO 17972-4, Graphic technology — Colour data

exchange format (CxF/X) — Part 4: Spot colour characterization data (CxF/X-4). ISO 17972-4 includes

exchange specifications for spot colour characterization data to facilitate the communication of spot

colour data.
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DRAFT INTERNATIONAL STANDARD ISO/DIS 12647-9:2020(E)
Graphic technology — Process control for the production
of half-tone colour separations, proof and production
prints —
Part 9:
Metal decoration printing processes using offset
lithography
1 Scope

This part of ISO 12647 specifies requirements for systems that are used to produce offset prints for

process colour reproduction on metallic substrates, which have been printed with a white coating. It is

intended for flat printed sheet metal applications (it does not cover shaped or pre-formed metal such as

pre-formed cans). Recommendations are provided with regard to appropriate test methods associated

with these requirements.

This part of ISO 12647 differs from the method used to produce an offset print on paper or board in

Part 2 in that it considers the colour values of a typical white coated metal substrate intended for metal

decoration, using offset lithography and substrates that are independent of backing colour.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 12647-1:2013, Graphic technology — Process control for the production of half-tone colour separations,

proof and production prints — Part 1: Parameters and measurement methods

ISO 12647-7:2016, Graphic technology — Process control for the production of halftone colour separations,

proof and production prints — Part 7: Proofing processes working directly from digital data

ISO 13655:2017, Graphic technology — Spectral measurement and colorimetric computation for graphic

arts images

ISO/TS 10128:2009, Graphic technology — Methods of adjustment of the colour reproduction of a printing

system to match a set of characterization data

ISO 17972-1:2018, Graphic technology — Colour data exchange format — Part 1: Relationship to CxF3 (CxF/X)

ISO 17972-4:2018, Graphic technology — Colour data exchange format (CxF/X) — Part 4: Spot colour

characterisation data (CxF/X-4)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 12647-1 and the following apply.

3.1
total print area
ratio of the area covered with ink to the entire area in an ink zone
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ISO/DIS 12647-9:2020(E)
3.2
characterization data

set of tone values and associated colorimetric values that fully describe a given printing process

3.3
metal decoration
printing on metals to produce a graphic image on the metal surface,

Note 1 to entry: The term does not exclude printing on metal for functional or promotional reasons

3.4
spot colour

non-process colour that is used in addition to, or in place of, a process colour and is normally applied

with a single impression

Note 1 to entry: When associated with a corporate product identity, a spot colour is also known as brand colour.

4 Requirements
4.1 General

Digital data files delivered for printing should be accompanied by a digital proof print, a press proof

print, or an OK print from a previous print run.

Note Press proof prints are test prints of the data files on a printing press which may serve as a reference

for subsequent printing. While most proofs are digital proofs, for colour- or content-critical work there is a need

for press proof prints with the same setup as the production print.
4.2 Data files and printing formes
4.2.1 Data delivery

Data delivered for printing shall be in the colour formats CMYK or three-component and should be

exchanged using PDF/X data formats.

The intended printing condition shall be indicated. In case of PDF/X the mechanisms provided by the

specified data format shall be used. In case of other data formats, a printing condition description, a

[3][4] [5]

characterization data set or an International Colour Consortium (ICC) output profile shall be

communicated.

If the data are other than CMYK, the data shall be defined by colorimetric descriptions using an ICC

profile or another mechanism and an ICC CMYK output profile shall be included. The rendering intent to

be used for each data element shall be communicated.

If the characterization data or ICC output profile provided conflicts with the printing conditions defined

in this part of ISO 12647 one of the methods defined in ISO/TS 10128 shall be used for data adjustment

prior to print production. The aims for process control should be taken from characterization data, if

agreed between all parties. Where this is done, densitometric tone values are not usually available and

colorimetric tone values should be used. Further information on the relationship between colorimetric

and densitometric tone values can be found in ISO/TS 10128.

Note 1 A printing condition is defined here as a print substrate description, a colorant description, a screening

description, an ink set and a printing sequence.

Note 2 Quality control of the content of a print job prior to final production checks are recommended since

PDF/X conformance does not necessarily ensure a suitable image resolution or other production dependent

criteria.

Note 3 Additional spot colours are allowed but this part of ISO 12647 does not make provisions for tolerances.

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ISO/DIS 12647-9:2020(E)
4.2.2 Printing forme quality

The resolution of the plate setter should be selected to ensure that at least 150 tone value steps are

reproduced.

EXAMPLE If, for a screen employing single half-tone cell modulation, the intended nominal screen ruling

is 80 cm−1, the resolution of the plate setter should not be less than 1 000 cm−1. For a screen with super-cell

technology, it is possible to set the resolution to a smaller value.
4.2.3 Screen frequency (periodic screens)

For four-colour work, the screen frequency (screen ruling) for periodic screens should be within the

−1 −1 -1

range from 48 cm to 80 cm ; 69 cm (175 lines per inch) is the most common plate frequency.

Note 1 The screen frequency is often varied slightly from one process colour to another in order to minimize

moiré patterns. For example, there might be a difference of up to 6 % of the nominal screen frequency between

the colours C, M, Y.

Note 2 For the black or yellow colour halftone, a screen frequency is sometimes used which is

substantially finer than the nominal screen ruling of the remaining colours, for example, 84 cm versus

60 cm .

Note 3 Screen frequencies are often required or given in lpi (lines per inch). To convert between screens per

cm and lines per inch a conversion factor of 2,54 should be used.

EXAMPLE The requirement 4.2.3 given in lpi will read as follows (rounded to commonly used integral

numbers): for four-colour work, the screen frequency (screen ruling) for periodic screens should be within the

range from 120 lpi to 200 lpi.
4.2.4 Dot size (non-periodic screens)

For four-colour work, the screen dot size for non-periodic screens shall be within the range 20 µm to 40

µm and should be within the range 20 µm to 30 µm.

Note Outside of the range 20 µm to 40 µm, the general principles specified in ISO 12647-1 remain valid but

specific values might differ.
4.2.5 Screen angle (periodic screens)

For half-tone dots without a principal axis, the nominal difference between the screen angles for cyan,

magenta and black should be 30°, with the screen angle of yellow separated at 15° from another colour.

The screen angle of the dominant colour should be 45°.

For half-tone dots with a principal axis, the nominal difference between screen angles for cyan, magenta

and black should be 60°, with the screen angle of yellow separated by 15° from another colour. The

screen angle of the dominant colour should be 45° or 135°.
4.2.6 Dot shape and its relationship to tone value (periodic screens)

For periodic screens, circular, square or elliptical half-tone dot shapes should be used. For half-tone

dots with elliptical dot shape, the first link-up should occur no lower than at 40 % tone value and the

second linkup no higher than at 60 % tone value.
4.2.7 Tone Value Sum

Tests should be run to determine tone value sum, depending on the printing equipment, and drying,

tone value sum can vary from 180- 300. This should be tested on production equipment.

Note Press problems might be encountered at high levels of tone value sum. There might be poor ink

trapping, back transfer and set-off due to insufficient ink drying.
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ISO/DIS 12647-9:2020(E)
4.2.8 Grey reproduction and grey balance

The tone values of cyan, magenta and yellow that lead to a visually neutral grey should be calculated

from the standard printing condition or actual printing condition or the associated profiles by the

following formula describing the grey reproduction (L*, a*, b*) with respect to a given substrate colour

(L*substrate, a*substrate, b* substrate) and solid CMY inks overprint (L* ) for each L* in the range

cmy
from L* substrate to L* :
cmy
 
10−×,85 LL−
substrate
 
aa=×
substrate
 
LL−
substratecmy
 
 
10−×,85 LL−
substrate
 
bb=×
substrate
 
LL−
substratecmy
 

Note 1 A single grey balance condition is usually not sufficient to ensure an achromatic colour for all print

substrates and printing inks that can be used with a given printing process. Therefore, the grey balance has to

be determined for each printing condition separately based on a well-defined grey reproduction. See Annex A for

more details.

Note 2 The grey balance of a given printing process can be used for process calibration and process control

as long as the tolerances for tone value increase and mid-tone spread as defined in Table 8 are not exceeded.

Note 3 The multiplying factor of 0,85 represents a visual adaptation of 85 % to the substrate white.

4.3 Proof or production print
4.3.1 General

A printing condition for sheet-fed offset printing shall be communicated by a print substrate description,

a colorant description, a screening description and a printing sequence.

Standard printing conditions are shown in Table 1. For all printing conditions described in this part of

ISO 12647 the printing sequence should be Black – Cyan – Magenta – Yellow.
Table 1 — Standard printing conditions for typical print substrates
Metal Printing Print Metal Colorant Screening description
condition substrate description
Periodic screens Non-periodic screens
(MPC) description (MCD)
TVI Frequency TVI Spot size
(Table 2) (Table 3)
curve (cm ) curve (μm)
MPC1 White MCD1 A 60 to 80 B 20 - 40
coated
150 – 200 (lpi)
metal
MPC2 White coated MCD2 C 60 TO 80 D 20 - 40
MPC3 metal
150 – 200
MPC4
(lpi)

Standard printing conditions are usually characterized by collecting (smoothing and averaging where

appropriate) colour measurement data from one or more printing presses that have been carefully set

up to a given printing condition. Such a collection of measurement data along with associated metadata

describing the characterized printing condition is known as a characterization data set. When such

characterization data are used to describe one of the printing conditions defined by this part of

ISO 12647 the print substrate, colorant, screening and printing sequence for the printing condition

from which the characterization data was collected shall be clearly indicated.

Note 1 Colorimetric characterization data, as specified in ISO 12642-1 and ISO 12642-2, contain all the data

to be specified in accordance with 4.3.2, 4.3.3, and 4.3.5.1 of this part of ISO 12647.

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ISO/DIS 12647-9:2020(E)

Note 2 A characterization data set or an ICC profile derived from it, is required when making proofs

according to ISO 12647-7. In practice this means that characterization data sets provide a convenient means for

the communication of standard printing conditions. Characterization data for standard printing conditions are

[1]
available from research or trade associations .

Note 3 Work separated for periodic screens can be printed using non-periodic screens where there is a moiré

problem on press. In some cases, moiré might introduce tone contouring artefacts and colour shift deficiencies in

primary and secondary half-tones.
4.3.2 Visual characteristics of image components - Print substrate colour

The print substrate used for press proof prints should be identical to that of the production print. If

this is not possible, the properties of the print substrate for press proof prints should be a close match

to those of the production print in terms of colour, CIE Whiteness, gloss, type of surface (coated with

white) and mass-per-area.

Evaluate the match of the press proof print substrate and the production print substrate using the

attributes listed in Table 2. For digital proofing, the requirements defined in ISO 12647-7 apply.

Typical substrate characteristics are defined, for information only, in Table 2. In order to determine the

closest matching printing condition for a given substrate type, compare the substrate to be used for

printing with the parameters in these tables and select the closest matching reference print substrate.

This procedure ensures an easy match of the associated colorant description and therefore the visual

appearance.

Production metallic substrates comprising a coloration differing from the aim values pertaining to

Table 2 may not be described by established data characterizations. In this case, a dedicated substrate

description using the attributes shown in Table 2, and an associated set of characterization data is

recommended.
Table 2 — CIELAB coordinates and CIE Whiteness for print substrates
(informative)
Metal Coating Type
— Characteristic
MC1 MC2 MC3 MC4
Type of surface White coating Pinkish coating Bluish Neutral coating
without varnish without varnish coating without without varnish
varnish
CIE Whiteness (D50/2°) 86 95 95 95
±4 ±5 ±10 ±10
Gloss (60°) 30 ± 20 80 ± 20 80 ± 20 80 ± 20
Coordinates
Colour (D50/2°)
L* a* b* L* a* b* L* a* b* L* a* b*
Aims 86 -2 -6 83 3 -8 81 -2 -9 89 -2 -3
Tolerance ±4 ±2 ±2 ±5 ±2 ±2 ±5 ±2 ±2 ±5 ±2 ±2
ASTM E 313 provides guidance on CIE white-
ness under other daylight illuminants
ISO13655: 2017 and Annex B describes how to
transform the primary colour targets on sub-
strates outside these tolerances.
4.3.3 Ink set colours (colorant description)

For the typical substrates defined in 4.3.2, the CIELAB colour coordinates of the process colour

solids shall agree with the aim values specified in Table 3, within the deviation tolerance specified

in Table 4. The colour coordinates of the two-colour overprints and the three-colour overprint, both

without black ink, should agree with Table 3. The tolerances on these colour aims can be found in Table

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ISO/DIS 12647-9:2020(E)

4 for the deviation from the production aim (OK sheet) and the variation within a print run from the

production prints.

Table 3 — CIELAB coordinates of colours for the printing sequence cyan-magenta-yellow

Colorant Description
MC1 MC2 MC3 MC4
Colour L* a* b* L* a* b* L* a* b* L* a* b*
Black 17 -1 0 8 1 2 8 1 1 5 1 2
Cyan 50 -32 -48 48 -30 -46 49 -32 -46 51 -37 -47
Magenta 42 64 -5 45 67 6 43 65 5 48 72 9
...