Graphic technology - Prepress digital data exchange - Colour targets for input scanner calibration - Part 1: Colour targets for input scanner calibration

This part of ISO 12641 defines the layout and colorimetric values of targets for use in the calibration of a photographic product/input scanner combination (as used in the preparatory process for printing and publishing). One target is defined for positive colour transparency film and another is defined for colour photographic paper.

Technologie graphique -- Échange de données numériques de préimpression -- Cibles de couleur pour étalonnage à l'entrée du scanner

Grafična tehnologija - Izmenjava digitalnih podatkov v grafični pripravi - Barvne tablice za umerjanje skenerjev - 1. del: Barvne tablice za umerjanje skenerjev

Ta del standarda ISO 12641 določa postavitev in vrednosti barvnih tablic, ki se uporabljajo pri umerjanju izdelkov za fotografiranje/skenerjev (kot se uporabljajo v pripravljalnem postopku tiskanja in objavljanja). Ena tablica je določena za barvno prosojnost pozitivnega filma, druga pa za barvni fotografski papir.

General Information

Status
Published
Publication Date
05-Feb-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
28-Jan-2020
Due Date
03-Apr-2020
Completion Date
06-Feb-2020

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INTERNATIONAL ISO
STANDARD 12641-1
First edition
2016-05-01
Graphic technology — Prepress digital
data exchange — Colour targets for
input scanner calibration —
Part 1:
Colour targets for input scanner
calibration
Technologie graphique — Échange de données numériques de
préimpression — Cibles de couleur pour étalonnage à l’entrée du
scanner
Reference number
ISO 12641-1:2016(E)
ISO 2016
---------------------- Page: 1 ----------------------
ISO 12641-1:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 12641-1:2016(E)
Contents Page

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

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

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

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

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

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Target design ............................................................................................................................................................................................ 4

4.2 Transmission targets ......................................................................................................................................................................... 4

4.2.1 Target layout and physical characteristics ................................................................................................ 4

4.2.2 Patch size ................................................................................................................................................................................ 9

4.2.3 Colour gamut mapping ............................................................................................................................................... 9

4.2.4 Neutral and dye scale values ..............................................................................................................................10

4.2.5 Neutral scale mapping .............................................................................................................................................11

4.3 Reflection targets ...............................................................................................................................................................................11

4.3.1 Target layout and physical characteristics .............................................................................................11

4.3.2 Patch size .............................................................................................................................................................................13

4.3.3 Colour gamut mapping ............................................................................................................................................14

4.3.4 Neutral and dye scale values ..............................................................................................................................14

4.3.5 Neutral scale mapping .............................................................................................................................................15

4.4 Allowable tolerances on patch values ..............................................................................................................................15

4.4.1 Uncalibrated targets ..................................................................................................................................................15

4.4.2 Calibrated targets .........................................................................................................................................................16

4.5 Spectral measurement and colorimetric calculation ..........................................................................................16

4.6 Data reporting ......................................................................................................................................................................................16

4.7 Data file format ....................................................................................................................................................................................16

4.7.1 File format ..........................................................................................................................................................................16

4.7.2 Keyword syntax and usage ...................................................................................................................................16

4.7.3 Data format identifiers ............................................................................................................................................17

4.8 Useable target life ..............................................................................................................................................................................19

Annex A (informative) Gamut mapping — Computational reference .............................................................................20

Annex B (informative) Application notes .....................................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................25

© ISO 2016 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 12641-1:2016(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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 130, Graphic technology.

This first edition of ISO 12641-1 cancels and replaces ISO 12641:1997, which has been technically revised

to take account of the technical advancements in the related fields and the associated equipment.

ISO 12641 consists of the following parts, under the general title Graphic technology — Prepress digital

data exchange:
— Part 1: Colour targets for input scanner calibration

An additional part dealing with advanced colour targets for input scanner calibration is planned.

Annexes A and B are for information only.
iv © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 12641-1:2016(E)
Introduction

The technical requirements of this part of ISO 12641 are identical to the American National Standards

IT8.7/1-1993 and IT8.7/2-1993. These Standards resulted from the joint efforts of an international

industry group that included participants representing a broad range of prepress vendors, film

manufacturers, and users. This group, initially identified as the digital data exchange standards (DDES)

committee, later became the founders of the ANSI IT8 (Image Technology) accredited standards

committee which is responsible for electronic data exchange standards in graphic arts prepress.

Purpose of this part of ISO 12641

Colour input scanners do not all analyse colour the same way the human eye does. These devices are

designed to optimize the signal generated when typical materials are scanned. Colour reflection and

transparency products use various combinations of proprietary dye sets to achieve visual responses

that simulate the colour appearance of natural scene elements. The ability to achieve the same

colour appearance from different combinations of dyes is referred to as metamerism. Because both

photographic dyes and input scanner sensitivities vary from product to product, there is variability

in the input scanner response to metameric colours produced by the various materials. The intent of

this part of ISO 12641 is to define an input test target that will allow any colour input scanner to be

calibrated with any film or paper dye set used to create the target. This part of ISO 12641 is intended

to address the colour reflection and transparency products which are generally used for input to the

preparatory process for printing and publishing.

The target was designed to be useable for calibration by visual comparison and as a numerical data

target for electronic systems and future development. The target design made use of a uniform colour

space to optimize the spacing of target patches. The tolerances developed for individual coloured

patches meet the values needed for both numerical and visual analysis.
Design of the target

The CIE 1976 (L*a*b*) or CIELAB colour space was chosen as the space to be used for the design of the

colour calibration target. Uniform spacing in hue angle, lightness and chroma, and tolerancing in terms

of differences in these parameters (∆E* ) is believed to provide a reasonable distribution of coloured

patches in the most effective manner. Although CIELAB was defined with reference to reflection

viewing conditions, tolerancing in terms of vector differences (∆E* ) does provide a reasonable error

estimate for transmission materials as well, although the uniformity of the space is dependent upon the

conditions of viewing.

The design goal was to define a target that would have, as its main part, as many common coloured

patches as was practical, regardless of the dye set used. The remainder of the target is intended to

define the unique colour characteristics of the particular dye set used to create a specific target; the

values for each target patch is to be established using a common procedure.

To provide a reasonable measure of the colour gamut that is within the capability of modern colour

papers and films, all manufacturers of these products were invited to provide colour dye data along

with the necessary minimum and maximum density data for each of their image forming colour dye

sets. Data were provided by Agfa Company, Eastman Kodak Company, Fuji Photo Film Company, and

Konica Corporation. These data were then used to estimate the CIELAB colour gamut that each paper

and film dye set could produce. This estimate was achieved by mathematical modelling (by several of

the participating companies) using methods which were different but gave very similar results. Annex A

provides additional reference material concerning the method used in selecting aim values.

The following documents provide reference information on the computational methods used in gamut

determination.

1. N. Ohta, “The Color Gamut Obtainable by the Combination of Subtractive Color Dyes. V. Optimum

Absorption Bands as Defined by Nonlinear Optimization Technique.” Journal of Imaging Science, 30,

[1]
9-12 (1986) .
© ISO 2016 – All rights reserved v
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ISO 12641-1:2016(E)

2. M. Inui, “Fast Algorithm for Computing Color Gamuts,” Colour Research and Application, 18, 341-348

[4]
(1993) .

All computations were based upon the use of the CIE 2 degree observer and D illuminant. All

transmission measurements were made using diffuse/normal or normal/diffuse geometry as defined

for total transmittance. All reflection measurements were made using 0°/45° or 45°/0° geometry

as defined in ISO 13655. The reference white was assumed to be a perfect diffuser. The use of an

absolute reference allows all colours on similar media (reflection or transmission) that have the same

colorimetric definition to also look the same when viewed at the same time.

The gamut plots developed were then used to determine the colour gamuts for film and paper that were

common to all of the provided dye families. The limiting values of chroma were then reduced to 80 % of

their computed values to create a “common gamut” for purposes of target design.

The goal was to have all coloured patches defined in the same way (regardless of the product used)

and to have as many patches as practical. The defined colour gamut therefore required a pattern with

a consistent reference. An existing colour input target provided by Eastman Kodak Company under the

designation of “Kodak Colour Reproduction Guides, Q-60™” was used as a guide in the development

of the target. The Q-60™ target used 12 approximately uniformly spaced hue angles in CIELAB. These

were sampled at three chroma values at each of three lightness levels. Although this pattern does not

provide equal spacing in terms of ∆E* , it does provide an easily understandable and defined patch

arrangement. It was adopted for these targets with the addition of a fourth product-specific chroma

value at each hue angle/lightness combination.

Lightness levels were chosen for each hue angle to best characterize the gamut at that hue angle. The

three common chroma values were then chosen such that one fell on the computed 80 % chroma limit

common to all the products and the others were equally spaced in chroma between this value and the

neutral. The fourth chroma, which is product-specific, was defined to be the maximum available from

each product at the specific hue angle and lightness level. This provided a consistent mapping for all

products.

It was also felt to be important to include scales in each of the individual dyes, dye pairs, and a dye

neutral along with areas to define product minimum and maximum densities.

A “vendor-optional” area was provided so that different target manufacturers could add unique patches

of their own determination beyond those which are required by this International Standard.

Manufacturing tolerances

In order to permit practical production of these targets, tolerances had to be set which were capable of

being achieved over a significant number of targets. However, this conflicted with the relatively narrow

tolerances required for numerical colour calibration. Different tolerances were therefore defined for

differing applications, with the objective of minimizing variations as far as was reasonable.

vi © ISO 2016 – All rights reserved
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 12641-1:2016(E)
Graphic technology — Prepress digital data exchange —
Colour targets for input scanner calibration —
Part 1:
Colour targets for input scanner calibration
1 Scope

This part of ISO 12641 defines the layout and colorimetric values of targets for use in the calibration

of a photographic product/input scanner combination (as used in the preparatory process for printing

and publishing). One target is defined for positive colour transparency film and another is defined for

colour photographic paper.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 1008, Photography — Paper dimensions — Pictorial sheets
ISO 1012, Photography — Films in sheets and rolls for general use — Dimensions

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

arts images
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
CIE tristimulus value

amount of the three reference colour stimuli, in the CIE-specified trichromatic system, required to

match the colour of the stimulus considered

Note 1 to entry: In the 1931 CIE standard colorimetric system, the tristimulus values are represented by the

symbols X, Y, Z.
3.2
CIELAB colour difference
CIE 1976 L*, a*, b* colour difference
∆E*

difference between two colour stimuli defined as the Euclidean distance between the points

representing them in L*, a*, b* space
 
22 2 2
Δ=EL** Δ +Δab**+Δ 
() () ()
 
 
where

∆L*, ∆a*, and ∆b* is the difference between corresponding values for the two stimuli.

© ISO 2016 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 12641-1:2016(E)
[SOURCE: International Lighting Vocabulary 845-03-55]
3.3
CIELAB colour space
CIE 1976 L*, a*, b* colour space

three-dimensional, approximately uniform, colour space produced by plotting in rectangular

coordinates the quantities L*, a*, and b* defined by the Formulae:
 
L* =116 f YY −16
 
 
 
a* = 500 fX Xf− YY
() ()
 
 
 
bf* = 200 YY −− fZ Z
() ()
 
n n
 
where for
XX >0,,008 856 f XX = XX
() ()
nn n
YY >0,,008 856 f YY = YY
() ()
nn n
ZZ >00,,008 856 fZ ZZ= Z
() ()
n nn
and for
XX >0,,008856 f XX =7,78671XX + 6 116
() ()
nn n
YY >0,,008856 fY Y =7,,78671YY + 6 116
() ()
nn n
ZZ >0,,008856 f ZZ =7,78671ZZ + 6 116
() ()
nn n
and
X =96,,422
Ya=100,000 nd
Zf=82,,521 or theconditionsofISO 136555.
Further
Ca**=+b*
and
hb= tan **a
where
09ϒϒ≤
b*≥0
90ϒϒ≤ b*>0
180ϒϒ≤ b*≤0
270ϒϒ≤ b*<0
[SOURCE: CIE Publication 15.2]
2 © ISO 2016 – All rights reserved
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ISO 12641-1:2016(E)
3.4
transmittance factor

ratio of the measured flux transmitted by the sample material to the measured flux when the sample

material is removed from the sampling aperture of the measuring device
3.5
transmission density
logarithm to base 10 of the reciprocal of the transmittance factor
3.6
reflectance factor

ratio of the measured flux reflected from the sample material to the flux reflected from a perfect

reflecting diffuser
3.7
reflection density
logarithm to base 10 of the reciprocal of the reflectance
3.8
colour gamut
subset of perceivable colours reproducible by a device or medium
3.9
dye set
combination of light absorbing dyes

Note 1 to entry: Usually referred to as cyan, magenta, and yellow. Used in a particular photographic product

which produce object colours by the selective subtraction of the incident light.
3.10
dye scale

array of physical areas having varying amounts of one or more (cyan, magenta, or yellow) dyes

3.11
neutral scale

array of physical areas having combination of dye amounts such that their chroma is equal to, or near, zero

3.12
metameric colour stimuli
spectrally different colour stimuli having the same tristimulus values
[SOURCE: International Lighting Vocabulary 845-03-05]
3.13
minimum density
Dmin

density corresponding to the maximum transmittance factor (film) or reflectance factor (paper) that a

photographic product can achieve

Note 1 to entry: It is not necessarily neutral in colour and should not be confused with minimum neutral density.

3.14
minimum neutral density

minimum density that a photographic product can achieve (maximum transmittance or reflectance

factors) and maintain a C* = 0
Note 1 to entry: It should not be confused with minimum density (Dmin).
© ISO 2016 – All rights reserved 3
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ISO 12641-1:2016(E)
3.15
maximum density
Dmax

density corresponding to the minimum transmittance or reflectance factor that a photographic product

can achieve

Note 1 to entry: It is not necessarily neutral in colour and should not be confused with maximum neutral density.

3.16
maximum neutral density

density corresponding to the maximum density that a photographic product can achieve (minimum

transmittance or reflectance factors) and maintain a C* = 0
Note 1 to entry: It should not be confused with maximum density (Dmax).
3.17
input scanner

device capable of converting the light reflectance or transmittance of a photographic (or other

hardcopy) sample into an electronic signal, where the electronic signal is arranged to have an organized

relationship to the spatial areas of the image evaluated
3.18
product-specific target areas

portions of the test target whose requirements are specifically defined, but whose values are a function

of the particular product used to make the target
3.19
vendor-optional target areas

portions of the test target whose content is not specified but is available for use by the manufacturer of

the target
4 Requirements

All colorimetry referenced within this part of ISO 12641 shall be based on D illuminant, CIE 1931

Standard Colorimetric Observer (2 degree observer) as defined in CIE 15.2, and computational

procedures further defined in 4.5. The reference white is the D illuminant.
4.1 Target design
The target is designed with five distinct sections. These are the following:
— sampled colour area;
— colour dye scales;
— neutral dye scale;
— Dmin/Dmax area;
— vendor-optional area.
4.2 Transmission targets
4.2.1 Target layout and physical characteristics

4.2.1.1 Type 1, 4 in × 5 in film: The layout of the Type 1 colour transmission input calibration target

as viewed from the support side of the film shall be as shown in Figure 1. This layout is intended for

use with film material having a size of 4 in × 5 in (10,2 cm × 12,7 cm) in accordance with ISO 1012.

All non-image areas of the target shall be approximately neutral and shall have a lightness of (L*) of

4 © ISO 2016 – All rights reserved
---------------------- Page: 10 ----------------------
ISO 12641-1:2016(E)

approximately 50. The non-image area shall extend at least 4,5 mm beyond the row and column borders

on the top and sides at least 10 mm on the bottom to provide for identification information.

ISO 12641-1:2016
2016:12
Figure 1 — Layout, Type 1 colour transmission target
ISO 12641-1:2016
2016:12
Figure 2 — Type 1 target, row, and column numbering

Target row and column numbering shall be of high density and as shown in Figure 2. Vertical lines

may be used to separate columns 12 and 13, 15, 16 and 17, and 19 and 20. Indicators may be used at

the intersection of target patches. These may be points, crosses, or other symbols, and may be of any

© ISO 2016 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO 12641-1:2016(E)

density or colour desired. If used, they shall be less than 0,3 mm in width. No other marking lines shall

be included within the body of the A1 through L19 portion of the target.

Lines shall be included to separate the Dmin area from the first step and the Dmax area from the last

step of the 22-step neutral scale along the bottom of the target.

Unless otherwise noted, all lines shall be neutral and have a lightness (L*) no greater than that specified

for the background.

Fiducial marks shall be included in each corner of the main body of the target as shown in Figure 3.

These shall be arranged such that they “point” towards the inside or centre of the target.

Because target patches are 4,5 mm × 4,5 mm in size (see 4.2.2), the intersection of the lines of the

fiducial marks shall be offset 4,5 mm in both the horizontal and vertical direction from the centre of the

nearest patch to provide a reference for automatic measurement alignment.

Fiducial marks shall be clear lines on the neutral background and shall be approximately 0,1 mm in width.

Figure 3 — Fiducial mark design

The area at the bottom of the target shall contain the following information in English text:

a) ISO 12641-1:2016;
b) the name of the film product or product family;
c) the year and month of production of the target in the form yyyy:mm;
d) an area of at least 10 mm × 25 mm for addition of a unique identification.

NOTE Targets bearing the designation IT8.7/1-1993 are prepared in accordance with ANSI IT8.7/1-1993

whose technical requirements are identical to those of this part of ISO 12641.
6 © ISO 2016 – All rights reserved
---------------------- Page: 12 ----------------------
ISO 12641-1:2016(E)

4.2.1.2 Type 2, 35 mm film: The Type 2 layout of the colour transmission input calibration target, as

viewed from the support side of the product, shall be as shown in Figure 4 (frames 35-1 through 35-7).

This layout is intended for use on film material having a basic format of 35 mm. This layout may be

provided either as a single strip of film or as seven mounted 35 mm transparencies.

The target shall be divided as follows:

Frame 35-1 The Dmin, neutral scale, and Dmax patches from the bottom of Type 1 target format

Frame 35-2 Columns 1 through 4 of the Type 1 target format
Frame 35-3 Columns 5 through 8 of the Type 1 target format
Frame 35-4 Columns 9 through 12 of the Type 1 target format
Frame 35-5 Columns 13 through 16 of the Type 1 target format
Frame 35-6 Columns 17 through 19 of the Type 1 target format
Frame 35-7 Columns 20 through 22 of the Type 1 target format

In addition, each frame shall have a six step neutral scale as column N with L* values as follows:

Step 1 82(top)
Step 2 66
Step 3 50
Step 4 34
Step 5 18
Step 6 2

All non-image areas of the target shall be approximately neutral and shall have a lightness (L*) of

approximately 50.

Each frame of the target shall contain the following information in English text:

a) ISO 12641-1:2016;
b) a frame number of the form 35-X;
c) the name of the film product or product family;
d) the year and month of production of the target in the form yyyy:mm.

NOTE Targets bearing the designation IT8.7/1-1993 are prepared in accordance with ANSI IT8.7/1-1993

whose technical requirements are identical to those of this part of ISO 12641.

If provided as individually mounted transparencies, this same information shall be repeated on the mount.

The frame numbering and reference lines shall be high in density and as shown in Figure 5.

© ISO 2016 – All rights reserved 7
---------------------- Page: 13 ----------------------
ISO 12641-1:2016(E)
Figure 4 — Layout, Type 2 colour transmission target
8 © ISO 2016 – All rights reserved
---------------------- Page: 14 ----------------------
ISO 12641-1:2016(E)
ISO 12641-1:2016
2016:12
Figure 5 — Type 2 target, row and column numbering

Divider lines shall be included in Frame 35-1 between Dmin and step 1 of the neutral scale, and step 22

of the neutral scale and Dmax.

Unless otherwise noted, all lines shall be neutral and have a lightness (L*) no greater than that specified

for background.

4.2.1.3 Type 3, 35 mm film version of Type 1 target (optional): A 35 mm version of the Type 1 target

may be provided at the discretion of the film vendor. If provided, it shall contain labelling information to

ensure that scanned data from the 35 mm version of the target cannot be confused with scanned data

from the full size version of the target. This target shall be a reduced size version of the Type 1 target, but

shall not be required t
...

SLOVENSKI STANDARD
SIST ISO 12641-1:2020
01-marec-2020
Nadomešča:
SIST ISO 12641:2002

Grafična tehnologija - Izmenjava digitalnih podatkov v grafični pripravi - Barvne

tablice za umerjanje skenerjev - 1. del: Barvne tablice za umerjanje skenerjev

Graphic technology - Prepress digital data exchange - Colour targets for input scanner

calibration - Part 1: Colour targets for input scanner calibration

Technologie graphique -- Échange de données numériques de préimpression -- Cibles

de couleur pour étalonnage à l'entrée du scanner
Ta slovenski standard je istoveten z: ISO 12641-1:2016
ICS:
35.240.30 Uporabniške rešitve IT v IT applications in information,
informatiki, dokumentiranju in documentation and
založništvu publishing
37.100.99 Drugi standardi v zvezi z Other standards related to
grafično tehnologijo graphic technology
SIST ISO 12641-1:2020 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 12641-1:2020
---------------------- Page: 2 ----------------------
SIST ISO 12641-1:2020
INTERNATIONAL ISO
STANDARD 12641-1
First edition
2016-05-01
Graphic technology — Prepress digital
data exchange — Colour targets for
input scanner calibration —
Part 1:
Colour targets for input scanner
calibration
Technologie graphique — Échange de données numériques de
préimpression — Cibles de couleur pour étalonnage à l’entrée du
scanner
Reference number
ISO 12641-1:2016(E)
ISO 2016
---------------------- Page: 3 ----------------------
SIST ISO 12641-1:2020
ISO 12641-1:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 12641-1:2020
ISO 12641-1:2016(E)
Contents Page

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

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

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

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

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

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Target design ............................................................................................................................................................................................ 4

4.2 Transmission targets ......................................................................................................................................................................... 4

4.2.1 Target layout and physical characteristics ................................................................................................ 4

4.2.2 Patch size ................................................................................................................................................................................ 9

4.2.3 Colour gamut mapping ............................................................................................................................................... 9

4.2.4 Neutral and dye scale values ..............................................................................................................................10

4.2.5 Neutral scale mapping .............................................................................................................................................11

4.3 Reflection targets ...............................................................................................................................................................................11

4.3.1 Target layout and physical characteristics .............................................................................................11

4.3.2 Patch size .............................................................................................................................................................................13

4.3.3 Colour gamut mapping ............................................................................................................................................14

4.3.4 Neutral and dye scale values ..............................................................................................................................14

4.3.5 Neutral scale mapping .............................................................................................................................................15

4.4 Allowable tolerances on patch values ..............................................................................................................................15

4.4.1 Uncalibrated targets ..................................................................................................................................................15

4.4.2 Calibrated targets .........................................................................................................................................................16

4.5 Spectral measurement and colorimetric calculation ..........................................................................................16

4.6 Data reporting ......................................................................................................................................................................................16

4.7 Data file format ....................................................................................................................................................................................16

4.7.1 File format ..........................................................................................................................................................................16

4.7.2 Keyword syntax and usage ...................................................................................................................................16

4.7.3 Data format identifiers ............................................................................................................................................17

4.8 Useable target life ..............................................................................................................................................................................19

Annex A (informative) Gamut mapping — Computational reference .............................................................................20

Annex B (informative) Application notes .....................................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................25

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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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 130, Graphic technology.

This first edition of ISO 12641-1 cancels and replaces ISO 12641:1997, which has been technically revised

to take account of the technical advancements in the related fields and the associated equipment.

ISO 12641 consists of the following parts, under the general title Graphic technology — Prepress digital

data exchange:
— Part 1: Colour targets for input scanner calibration

An additional part dealing with advanced colour targets for input scanner calibration is planned.

Annexes A and B are for information only.
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Introduction

The technical requirements of this part of ISO 12641 are identical to the American National Standards

IT8.7/1-1993 and IT8.7/2-1993. These Standards resulted from the joint efforts of an international

industry group that included participants representing a broad range of prepress vendors, film

manufacturers, and users. This group, initially identified as the digital data exchange standards (DDES)

committee, later became the founders of the ANSI IT8 (Image Technology) accredited standards

committee which is responsible for electronic data exchange standards in graphic arts prepress.

Purpose of this part of ISO 12641

Colour input scanners do not all analyse colour the same way the human eye does. These devices are

designed to optimize the signal generated when typical materials are scanned. Colour reflection and

transparency products use various combinations of proprietary dye sets to achieve visual responses

that simulate the colour appearance of natural scene elements. The ability to achieve the same

colour appearance from different combinations of dyes is referred to as metamerism. Because both

photographic dyes and input scanner sensitivities vary from product to product, there is variability

in the input scanner response to metameric colours produced by the various materials. The intent of

this part of ISO 12641 is to define an input test target that will allow any colour input scanner to be

calibrated with any film or paper dye set used to create the target. This part of ISO 12641 is intended

to address the colour reflection and transparency products which are generally used for input to the

preparatory process for printing and publishing.

The target was designed to be useable for calibration by visual comparison and as a numerical data

target for electronic systems and future development. The target design made use of a uniform colour

space to optimize the spacing of target patches. The tolerances developed for individual coloured

patches meet the values needed for both numerical and visual analysis.
Design of the target

The CIE 1976 (L*a*b*) or CIELAB colour space was chosen as the space to be used for the design of the

colour calibration target. Uniform spacing in hue angle, lightness and chroma, and tolerancing in terms

of differences in these parameters (∆E* ) is believed to provide a reasonable distribution of coloured

patches in the most effective manner. Although CIELAB was defined with reference to reflection

viewing conditions, tolerancing in terms of vector differences (∆E* ) does provide a reasonable error

estimate for transmission materials as well, although the uniformity of the space is dependent upon the

conditions of viewing.

The design goal was to define a target that would have, as its main part, as many common coloured

patches as was practical, regardless of the dye set used. The remainder of the target is intended to

define the unique colour characteristics of the particular dye set used to create a specific target; the

values for each target patch is to be established using a common procedure.

To provide a reasonable measure of the colour gamut that is within the capability of modern colour

papers and films, all manufacturers of these products were invited to provide colour dye data along

with the necessary minimum and maximum density data for each of their image forming colour dye

sets. Data were provided by Agfa Company, Eastman Kodak Company, Fuji Photo Film Company, and

Konica Corporation. These data were then used to estimate the CIELAB colour gamut that each paper

and film dye set could produce. This estimate was achieved by mathematical modelling (by several of

the participating companies) using methods which were different but gave very similar results. Annex A

provides additional reference material concerning the method used in selecting aim values.

The following documents provide reference information on the computational methods used in gamut

determination.

1. N. Ohta, “The Color Gamut Obtainable by the Combination of Subtractive Color Dyes. V. Optimum

Absorption Bands as Defined by Nonlinear Optimization Technique.” Journal of Imaging Science, 30,

[1]
9-12 (1986) .
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2. M. Inui, “Fast Algorithm for Computing Color Gamuts,” Colour Research and Application, 18, 341-348

[4]
(1993) .

All computations were based upon the use of the CIE 2 degree observer and D illuminant. All

transmission measurements were made using diffuse/normal or normal/diffuse geometry as defined

for total transmittance. All reflection measurements were made using 0°/45° or 45°/0° geometry

as defined in ISO 13655. The reference white was assumed to be a perfect diffuser. The use of an

absolute reference allows all colours on similar media (reflection or transmission) that have the same

colorimetric definition to also look the same when viewed at the same time.

The gamut plots developed were then used to determine the colour gamuts for film and paper that were

common to all of the provided dye families. The limiting values of chroma were then reduced to 80 % of

their computed values to create a “common gamut” for purposes of target design.

The goal was to have all coloured patches defined in the same way (regardless of the product used)

and to have as many patches as practical. The defined colour gamut therefore required a pattern with

a consistent reference. An existing colour input target provided by Eastman Kodak Company under the

designation of “Kodak Colour Reproduction Guides, Q-60™” was used as a guide in the development

of the target. The Q-60™ target used 12 approximately uniformly spaced hue angles in CIELAB. These

were sampled at three chroma values at each of three lightness levels. Although this pattern does not

provide equal spacing in terms of ∆E* , it does provide an easily understandable and defined patch

arrangement. It was adopted for these targets with the addition of a fourth product-specific chroma

value at each hue angle/lightness combination.

Lightness levels were chosen for each hue angle to best characterize the gamut at that hue angle. The

three common chroma values were then chosen such that one fell on the computed 80 % chroma limit

common to all the products and the others were equally spaced in chroma between this value and the

neutral. The fourth chroma, which is product-specific, was defined to be the maximum available from

each product at the specific hue angle and lightness level. This provided a consistent mapping for all

products.

It was also felt to be important to include scales in each of the individual dyes, dye pairs, and a dye

neutral along with areas to define product minimum and maximum densities.

A “vendor-optional” area was provided so that different target manufacturers could add unique patches

of their own determination beyond those which are required by this International Standard.

Manufacturing tolerances

In order to permit practical production of these targets, tolerances had to be set which were capable of

being achieved over a significant number of targets. However, this conflicted with the relatively narrow

tolerances required for numerical colour calibration. Different tolerances were therefore defined for

differing applications, with the objective of minimizing variations as far as was reasonable.

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Graphic technology — Prepress digital data exchange —
Colour targets for input scanner calibration —
Part 1:
Colour targets for input scanner calibration
1 Scope

This part of ISO 12641 defines the layout and colorimetric values of targets for use in the calibration

of a photographic product/input scanner combination (as used in the preparatory process for printing

and publishing). One target is defined for positive colour transparency film and another is defined for

colour photographic paper.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 1008, Photography — Paper dimensions — Pictorial sheets
ISO 1012, Photography — Films in sheets and rolls for general use — Dimensions

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

arts images
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
CIE tristimulus value

amount of the three reference colour stimuli, in the CIE-specified trichromatic system, required to

match the colour of the stimulus considered

Note 1 to entry: In the 1931 CIE standard colorimetric system, the tristimulus values are represented by the

symbols X, Y, Z.
3.2
CIELAB colour difference
CIE 1976 L*, a*, b* colour difference
∆E*

difference between two colour stimuli defined as the Euclidean distance between the points

representing them in L*, a*, b* space
 
22 2 2
Δ=EL** Δ +Δab**+Δ 
() () ()
 
 
where

∆L*, ∆a*, and ∆b* is the difference between corresponding values for the two stimuli.

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[SOURCE: International Lighting Vocabulary 845-03-55]
3.3
CIELAB colour space
CIE 1976 L*, a*, b* colour space

three-dimensional, approximately uniform, colour space produced by plotting in rectangular

coordinates the quantities L*, a*, and b* defined by the Formulae:
 
L* =116 f YY −16
 
 
 
a* = 500 fX Xf− YY
() ()
 
 
 
bf* = 200 YY −− fZ Z
() ()
 
n n
 
where for
XX >0,,008 856 f XX = XX
() ()
nn n
YY >0,,008 856 f YY = YY
() ()
nn n
ZZ >00,,008 856 fZ ZZ= Z
() ()
n nn
and for
XX >0,,008856 f XX =7,78671XX + 6 116
() ()
nn n
YY >0,,008856 fY Y =7,,78671YY + 6 116
() ()
nn n
ZZ >0,,008856 f ZZ =7,78671ZZ + 6 116
() ()
nn n
and
X =96,,422
Ya=100,000 nd
Zf=82,,521 or theconditionsofISO 136555.
Further
Ca**=+b*
and
hb= tan **a
where
09ϒϒ≤
b*≥0
90ϒϒ≤ b*>0
180ϒϒ≤ b*≤0
270ϒϒ≤ b*<0
[SOURCE: CIE Publication 15.2]
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3.4
transmittance factor

ratio of the measured flux transmitted by the sample material to the measured flux when the sample

material is removed from the sampling aperture of the measuring device
3.5
transmission density
logarithm to base 10 of the reciprocal of the transmittance factor
3.6
reflectance factor

ratio of the measured flux reflected from the sample material to the flux reflected from a perfect

reflecting diffuser
3.7
reflection density
logarithm to base 10 of the reciprocal of the reflectance
3.8
colour gamut
subset of perceivable colours reproducible by a device or medium
3.9
dye set
combination of light absorbing dyes

Note 1 to entry: Usually referred to as cyan, magenta, and yellow. Used in a particular photographic product

which produce object colours by the selective subtraction of the incident light.
3.10
dye scale

array of physical areas having varying amounts of one or more (cyan, magenta, or yellow) dyes

3.11
neutral scale

array of physical areas having combination of dye amounts such that their chroma is equal to, or near, zero

3.12
metameric colour stimuli
spectrally different colour stimuli having the same tristimulus values
[SOURCE: International Lighting Vocabulary 845-03-05]
3.13
minimum density
Dmin

density corresponding to the maximum transmittance factor (film) or reflectance factor (paper) that a

photographic product can achieve

Note 1 to entry: It is not necessarily neutral in colour and should not be confused with minimum neutral density.

3.14
minimum neutral density

minimum density that a photographic product can achieve (maximum transmittance or reflectance

factors) and maintain a C* = 0
Note 1 to entry: It should not be confused with minimum density (Dmin).
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3.15
maximum density
Dmax

density corresponding to the minimum transmittance or reflectance factor that a photographic product

can achieve

Note 1 to entry: It is not necessarily neutral in colour and should not be confused with maximum neutral density.

3.16
maximum neutral density

density corresponding to the maximum density that a photographic product can achieve (minimum

transmittance or reflectance factors) and maintain a C* = 0
Note 1 to entry: It should not be confused with maximum density (Dmax).
3.17
input scanner

device capable of converting the light reflectance or transmittance of a photographic (or other

hardcopy) sample into an electronic signal, where the electronic signal is arranged to have an organized

relationship to the spatial areas of the image evaluated
3.18
product-specific target areas

portions of the test target whose requirements are specifically defined, but whose values are a function

of the particular product used to make the target
3.19
vendor-optional target areas

portions of the test target whose content is not specified but is available for use by the manufacturer of

the target
4 Requirements

All colorimetry referenced within this part of ISO 12641 shall be based on D illuminant, CIE 1931

Standard Colorimetric Observer (2 degree observer) as defined in CIE 15.2, and computational

procedures further defined in 4.5. The reference white is the D illuminant.
4.1 Target design
The target is designed with five distinct sections. These are the following:
— sampled colour area;
— colour dye scales;
— neutral dye scale;
— Dmin/Dmax area;
— vendor-optional area.
4.2 Transmission targets
4.2.1 Target layout and physical characteristics

4.2.1.1 Type 1, 4 in × 5 in film: The layout of the Type 1 colour transmission input calibration target

as viewed from the support side of the film shall be as shown in Figure 1. This layout is intended for

use with film material having a size of 4 in × 5 in (10,2 cm × 12,7 cm) in accordance with ISO 1012.

All non-image areas of the target shall be approximately neutral and shall have a lightness of (L*) of

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approximately 50. The non-image area shall extend at least 4,5 mm beyond the row and column borders

on the top and sides at least 10 mm on the bottom to provide for identification information.

ISO 12641-1:2016
2016:12
Figure 1 — Layout, Type 1 colour transmission target
ISO 12641-1:2016
2016:12
Figure 2 — Type 1 target, row, and column numbering

Target row and column numbering shall be of high density and as shown in Figure 2. Vertical lines

may be used to separate columns 12 and 13, 15, 16 and 17, and 19 and 20. Indicators may be used at

the intersection of target patches. These may be points, crosses, or other symbols, and may be of any

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density or colour desired. If used, they shall be less than 0,3 mm in width. No other marking lines shall

be included within the body of the A1 through L19 portion of the target.

Lines shall be included to separate the Dmin area from the first step and the Dmax area from the last

step of the 22-step neutral scale along the bottom of the target.

Unless otherwise noted, all lines shall be neutral and have a lightness (L*) no greater than that specified

for the background.

Fiducial marks shall be included in each corner of the main body of the target as shown in Figure 3.

These shall be arranged such that they “point” towards the inside or centre of the target.

Because target patches are 4,5 mm × 4,5 mm in size (see 4.2.2), the intersection of the lines of the

fiducial marks shall be offset 4,5 mm in both the horizontal and vertical direction from the centre of the

nearest patch to provide a reference for automatic measurement alignment.

Fiducial marks shall be clear lines on the neutral background and shall be approximately 0,1 mm in width.

Figure 3 — Fiducial mark design

The area at the bottom of the target shall contain the following information in English text:

a) ISO 12641-1:2016;
b) the name of the film product or product family;
c) the year and month of production of the target in the form yyyy:mm;
d) an area of at least 10 mm × 25 mm for addition of a unique identification.

NOTE Targets bearing the designation IT8.7/1-1993 are prepared in accordance with ANSI IT8.7/1-1993

whose technical requirements are identical to those of this part of ISO 12641.
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4.2.1.2 Type 2, 35 mm film: The Type 2 layout of the colour transmission input calibration target, as

viewed from the support side of the product, shall be as shown in Figure 4 (frames 35-1 through 35-7).

This layout is intended for use on film material having a basic format of 35 mm. This layout may be

provided either as a single strip of film or as seven mounted 35 mm transparencies.

The target shall be divided as follows:

Frame 35-1 The Dmin, neutral scale, and Dmax patches from the bottom of Type 1 target format

Frame 35-2 Columns 1 through 4 of the Type 1 target format
Frame 35-3 Columns 5 through 8 of the Type 1 target format
Frame 35-4 Columns 9 through 12 of the Type 1 target format
Frame 35-5 Columns 13 through 16 of the Type 1 target format
Frame 35-6 Columns 17 through 19 of the Type 1 target format
Frame 35-7 Columns 20 through 22 of the Type 1 target format

In addition, each frame shall have a six step neutral scale as column N with L* values as follows:

Step 1 82(top)
Step 2 66
Step 3 50
Step 4 34
Step 5 18
Step 6 2

All non-image areas of the target shall be approximately neutral and shall have a lightness (L*) of

approximately 50.

Each frame of the target shall contain the following information in English text:

a) ISO 12641-1:2016;
b) a frame number of the form 35-X;
c) the name of the film product or product family;
d) the year and month of production of the target in the form yyyy:mm.
NOTE Targets bearing the designation IT8.7/1-1993
...

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