ISO 12641-1:2025

International
Standard
ISO 12641-1
Second edition
Graphic technology — Prepress
2025-02
digital data exchange —
Part 1:
Colour targets for input scanner
calibration
Technologie graphique — Échange de données numériques de
préimpression —
Partie 1: Cibles de couleur pour l'étalonnage des scanners en entrée
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 4
4.1 General .4
4.2 Target design .4
4.3 Transmission targets .4
4.3.1 Target layout and physical characteristics .4
4.3.2 Patch size . .10
4.3.3 Colour gamut mapping .11
4.3.4 Neutral and dye scale values .11
4.3.5 Neutral scale mapping . 12
4.4 Reflection targets . 13
4.4.1 Target layout and physical characteristics . 13
4.4.2 Patch size . . 15
4.4.3 Colour gamut mapping . 15
4.4.4 Neutral and dye scale values . 15
4.4.5 Neutral scale mapping .16
4.5 Allowable tolerances on patch values .17
4.5.1 Uncalibrated targets .17
4.5.2 Calibrated targets .17
4.6 Spectral measurement and colorimetric calculation .17
4.7 Data reporting .18
4.8 Data file format .18
4.8.1 File format .18
4.8.2 Keyword syntax and usage .18
4.8.3 Data format identifiers.19
4.9 Useable target life . 20
Annex A (informative) Gamut mapping — Computational reference .21
Annex B (informative) Application notes .23
Bibliography .26

iii
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
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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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.
This second edition cancels and replaces the first edition (ISO 12641-1:2016), which has been technically
revised.
The main changes are as follows:
— the title has been changed to align with the ISO/IEC Directives Part 2;
— some subclauses have been corrected;
— the normative references (see Clause 2) have been updated;
— the terms and definitions (see Clause 3) have been updated.
A list of all parts in the ISO 12641 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.

iv
Introduction
0.1  General
The technical requirements of this document 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.
0.2  Purpose of this document
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 document 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 document 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.
0.3  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
ab
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
ab
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.
References [15] and [16] provide reference information on the computational methods used in gamut
determination.
...