Graphic technology -- Prepress digital data exchange

ISO 12640-5:2013 specifies a set of standard scene-referred colour images (encoded as 16-bit RIMM RGB digital data) that can be used to evaluate transforms from a scene-referred image state to an output-referred image state (colour rendering transforms). They can be used for research, testing and assessing colour rendering transforms, in systems such as digital cameras, camera raw processing applications, colour management systems, colour profiles, and output devices such as displays and printers.

Technologie graphique -- Échange de données numériques de préimpression

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Status
Published
Publication Date
10-Dec-2013
Current Stage
6060 - International Standard published
Start Date
02-Dec-2013
Completion Date
11-Dec-2013
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INTERNATIONAL ISO
STANDARD 12640-5
First edition
2013-12-15
Graphic technology — Prepress digital
data exchange —
Part 5:
Scene-referred standard colour image
data (RIMM/SCID)
Technologie graphique — Échange de données numériques de
préimpression —
Partie 5: Données d’image standard en couleurs montrées en
référence par scène (RIMM/SCID)
Reference number
ISO 12640-5:2013(E)
ISO 2013
---------------------- Page: 1 ----------------------
ISO 12640-5:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

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

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Published in Switzerland
ii © ISO 2013 – All rights reserved
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ISO 12640-5:2013(E)
Contents Page

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

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

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

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

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

4 Data description .................................................................................................................................................................................................... 4

4.1 General ........................................................................................................................................................................................................... 4

4.2 Data set definition ................................................................................................................................................................................ 4

4.3 Image data arrangement ................................................................................................................................................................ 4

4.4 Data colour encoding ......................................................................................................................................................................... 4

4.5 Natural images ........................................................................................................................................................................................ 5

4.6 Synthetic images .................................................................................................................................................................................19

5 Electronic data .....................................................................................................................................................................................................23

Annex A (normative) Guidance for use of digital data ....................................................................................................................25

Annex B (normative) Check-sum data .............................................................................................................................................................27

Annex C (informative) Typical TIFF/IT file header used for image files ......................................................................29

Annex D (informative) Label text insertion ................................................................................................................................................31

Annex E (informative) Histogram and colour gamut ........................................................................................................................33

Bibliography .............................................................................................................................................................................................................................49

© ISO 2013 – All rights reserved iii
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ISO 12640-5:2013(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 Technical Committee ISO/TC 130, Graphic technology.

ISO 12640 consists of the following parts, under the general title Graphic technology — Prepress digital

data exchange:
— Part 1: CMYK standard colour image data (CMYK/SCID)
— Part 2: XYZ/sRGB standard colour image data (XYZ/SCID)
— Part 3: CIELAB standard colour image data (CIELAB/SCID)

— Part 4: Wide gamut display-referred standard colour image data (Adobe RGB(1998)/SCID)

— Part 5: Scene-referred standard colour image data (RIMM/SCID)
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ISO 12640-5:2013(E)
Introduction
0.1 Need for standard colour image data

Standard colour image data provide a set of data that can be used for any of the following tasks:

— evaluating the colour reproduction of imaging systems;
— evaluating colour image output devices;
— evaluating the effect of image processing algorithms applied to the images;

— evaluating the coding technologies necessary for the storage and transmission of high-definition

image data, etc.

These standard, well-defined image data sets, are typical of the high quality image content commonly

encountered when capturing and printing images. Users can therefore be confident that the images

should produce good quality reproductions if properly rendered, and that they provide a reasonable

test of the evaluation task being undertaken. No limited set of images can fully test any system, but the

sets provided give as reasonable a test as can be expected from a limited image set. Furthermore, the

existence of a standard set enables users in different locations to produce comparisons without the need

to exchange images prior to reproduction.

Different applications require that the standard image data be provided in different image states

using different image encodings (see ISO 22028-1), so the user needs to select those appropriate to

the evaluation task being undertaken. While transformation of the image data to another image state

is always possible, there is, in general, no agreement amongst experts as to how this should be done.

Thus, it has been considered preferable to provide data in different image states in the various parts of

ISO 12640. The relationship between image states is shown in Figure 1 along with the applicable parts

of ISO 12640.
© ISO 2013 – All rights reserved v
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ISO 12640-5:2013(E)
Figure 1 — Relationship between image states

ISO 12640-1 provides a set of 8 bits/channel data that is defined in terms of CMYK dot percentages.

The colours resulting from reproduction of CMYK data are strictly defined only at the time of printing,

and as such the data are only applicable to evaluation of CMYK printing applications. Transformations

to other image states and colour encodings might not be well defined. In fact, the data might not even

be useful for CMYK printing processes different from those typically found in traditional graphic arts

applications, as the image data are defined to produce “pleasing” images when reproduced on systems

using “typical” inks and producing “typical” tone value rendering. Printing systems that use inks of a

distinctly different colour, or produce a very different tone value rendering, will not reproduce them

as pleasing images without a well-defined colour transformation. Moreover, with a bit depth of only 8

bits/channel, any colour transformation employed might well introduce artefacts.

ISO 12640-2 provides a set of test image data encoded both as XYZ values with each channel scaled to the

range 0-65535, and as sRGB (defined in IEC 61966-2-1), with a bit depth of 8 bits/channel. (The higher bit

depth for the XYZ encoding is necessary because of the perceptual non-uniformity of the linear colour

space.) Both sets of data are optimized for viewing on a reference sRGB display in the reference sRGB

viewing environment, and relative to CIE standard illuminant D65 for which the XYZ tristimulus values

were computed prior to scaling. The images are mainly designed to be used on systems utilizing sRGB

as the reference encoding, and as such are primarily applicable to systems for which a colour monitor

similar to the sRGB reference display is the “hub” device. Although such systems are used for consumer

photography, they are less popular in the graphic arts industry because the sRGB colour gamut is quite

different in shape from the colour gamut of typical offset printing. This difference can necessitate fairly

aggressive colour re-rendering to produce optimal prints from sRGB image data.

ISO 12640-3 provides a set of test image data with a large reflection medium colour gamut, illuminated

using illuminant D50. The bit depth of the natural images is 16 bits/channel, while the colour charts and

vi © ISO 2013 – All rights reserved
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ISO 12640-5:2013(E)

vignettes are 8 bits/channel. In order to be useful for applications where large, print-referred output

gamuts are encountered, common in graphic technology and photography, it was felt that it would

be desirable to produce an image set in which some colours are permitted to be encoded close to the

boundary of the full colour gamut attained with surface colours. Furthermore, from the perspective

of colour management, it is advantageous if the images are referenced to illuminant D50, which is

the predominant reference illuminant used in graphic arts and photography, both for viewing and

measurement. For this reason, it has also become the predominant reference illuminant for most colour

management applications.

ISO 12640-4 provides a set of wide-gamut test image data encoded as Adobe RGB with a bit depth of

16 bits/channel. These data are optimized for viewing on a reference Adobe RGB display in the reference

Adobe RGB viewing environment (defined in the Adobe RGB (1998) Colour Image Encoding specification).

The images are designed to be used mainly on systems utilizing Adobe RGB as the reference encoding,

and as such are mainly applicable to the professional market and those systems for which the wide gamut

colour monitor is the “hub” device. Such workflows are popular among professional photographers,

and are increasingly used in the graphic arts. The Adobe RGB reference display colour gamut is closer

to typical offset printing gamuts than the sRGB reference display colour gamut. Adobe RGB encoded

images generally require much less aggressive colour re-rendering going to print than sRGB encoded

images, although this difference can necessitate colour re-rendering between Adobe RGB images and

sRGB images. The purpose of ISO 12640-4 is therefore to provide a test image data set with a larger

colour gamut than sRGB, related to the Adobe RGB wide-gamut display-referred colour space. The bit

depth of the natural images and synthetic images is 16 bits/channel.

The possible wide gamut colour encoding choices considered were Adobe RGB, opRGB (IEC 61966-2-5)

and ROMM RGB (ISO 22028-2). For ISO 12640-4, it was important that the images were well-colour-

rendered to a well-defined large gamut reference display, for which reason Adobe RGB was preferred

over the other two choices. With opRGB, the completeness of the colour rendering is left more ambiguous,

i.e. it is not as clearly output-referred, and the reference medium and viewing conditions are also

slightly different. ROMM RGB (ISO 22028-2) is clearly output-referred, but the reference medium is a

virtual reflection print (the ICC perceptual reference medium), so the image state is identical to that for

ISO 12640-3.

This part of ISO 12640 provides a set of scene-referred test image data encoded as RIMM RGB with a bit

depth of 16 bits/channel. These data are estimates of scene colorimetry obtained by capturing natural

scenes using a variety of digital cameras and transforming the captured raw camera RGB signals to

scene colorimetry estimates. The accuracy of these estimates is influenced by a number of factors

including the degree to which the camera spectral sensitivities approximate human visual system

colour matching functions, the appropriateness of the transformation from raw camera RGB signals to

colorimetry estimates, optical effects such as off-axis decrease in signal, aberrations and flare, and the

noise present in the camera signals. The transformations applied to obtain the colorimetry estimates

were general transformations, i.e. they were not optimized for the spectral characteristics of each scene.

Consequently, there can in some cases be significant errors in the estimates. The image state of these

data is scene-referred because no attempt has been made to colour render the data to produce a pleasing

reproduction on some output medium. The only processing applied to these data based on visual

evaluation was to select the scene adopted white. This was accomplished by applying gains individually

to the camera channels to achieve the desired white balance, converting to scene-referred, and then

adjusting the overall gain in a linear, scene-referred working space while viewing the image with the

example colour rendering transform specified in ISO/TS 22028-3:2012, Annex A, applied. Different

white balances can be desired in some cases for aesthetic reasons, and different overall gains can be

needed if different colour rendering transforms are used. The images provided in this part of ISO 12640

are mainly applicable for evaluating colour rendering to different output media.
0.2 Characteristics of the test images

The performance of any colour reproduction system will normally be evaluated both subjectively (by

viewing the final output image) and objectively (by measurement of control elements). This requirement

dictates that the test images include both natural scenes (pictures) and synthetic images (colour charts

and colour vignettes). Because the results of subjective image evaluation are strongly affected by the

image content, it was important to ensure that the natural images were of high quality and contained

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ISO 12640-5:2013(E)

diverse subject matter. However, it is difficult within a single, relatively small, sample set to produce

elements in the scene that contain all the subtle colour differences required in test images, and that

span the full range of colours that can be encountered in real scenes. For this reason, synthetic colour

charts are also included. These colour charts are limited by the integer RIMM RGB encoding and by

the spectral locus (for areas where the RIMM RGB encoding extends outside the spectral locus). In the

future, it is proposed to develop a second set of floating point RIMM/SCID which are not limited by the

integer RIMM RGB encoding.

To obtain the images, a survey was conducted of all TC 130 member countries to identify desirable

image content and to solicit submission of suitable images for consideration. The image set that resulted

consists of 44 natural images, two colour charts and a series of colour vignettes. The natural images

include flesh tones, hair, foliage, water, sky, flowers and other memory colours in scenes with a variety

of dynamic ranges.
0.3 File format of the digital test images

All of the images consist of pixel interleaved data (R then G then B), with the data origin at the upper

left of the image, as viewed naturally, and organized by rows. These data are included as individual files

within this part of ISO 12640. The image file format is as specified in ISO 12639 (TIFF/IT). A RIMM RGB

ICC profile meeting the requirements of ISO 15076-1 is embedded in each image file.

The images can be imported and manipulated as necessary by a wide variety of commonly used imaging

software tools and platforms in general use in the industry. (See Annex C for details of the TIFF header

and the RIMM RGB ICC profile.)
viii © ISO 2013 – All rights reserved
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INTERNATIONAL STANDARD ISO 12640-5:2013(E)
Graphic technology — Prepress digital data exchange —
Part 5:
Scene-referred standard colour image data (RIMM/SCID)
1 Scope

This part of ISO 12640 specifies a set of standard scene-referred colour images (encoded as 16-bit RIMM

RGB digital data) that can be used to evaluate transforms from a scene-referred image state to an output-

referred image state (colour rendering transforms). They can be used for research, testing and assessing

colour rendering transforms, in systems such as digital cameras, camera raw processing applications,

colour management systems, colour profiles, and output devices such as displays and printers.

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 12639:2004, Graphic technology — Prepress digital data exchange — Tag image file format for image

technology (TIFF/IT)

ISO/TS 22028-3:2012, Photography and graphic technology — Extended colour encodings for digital

image storage, manipulation and interchange — Part 3: Reference input medium metric RGB colour image

encoding (RIMM RGB)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
additive RGB colour space

colorimetric colour space having three colour primaries (generally red, green and blue) such that CIE

XYZ tristimulus values can be determined from the RGB colour space values by forming a weighted

combination of the CIE XYZ tristimulus values for the individual colour primaries, where the weights are

proportional to the radiometrically linear colour space values for the corresponding colour primaries

Note 1 to entry: A simple linear 3 × 3 transformation can be used to transform between CIE XYZ tristimulus

values and the radiometrically linear colour space values for an additive RGB colour space.

Note 2 to entry: Additive RGB colour spaces are defined by specifying the CIE chromaticity values for a set of

additive RGB primaries and a colour space white point, together with a colour component transfer function.

[SOURCE: ISO 22028-1:2004, 3.3]
3.2
adopted white

spectral radiance distribution as seen by an image capture or measurement device and converted to

colour signals that are considered to be perfectly achromatic and to have an observer adaptive luminance

factor of unity; i.e. colour signals that are considered to correspond to a perfect white diffuser

Note 1 to entry: The adopted white may vary within a scene.
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ISO 12640-5:2013(E)

Note 2 to entry: No assumptions should be made concerning the relation between the adapted or adopted white

and measurements of near perfectly reflecting diffusers in a scene, because measurements of such diffusers will

depend on the illumination and viewing geometry, and other elements in the scene that may affect perception.

It is easy to arrange conditions for which a near perfectly reflecting diffuser will appear to be grey or coloured.

[SOURCE: ISO 22028-1:2004, 3.4]
3.3
colour component transfer function
CCTF

single variable, monotonic mathematical function applied individually to one or more colour channels

of a colour space

Note 1 to entry: Colour component transfer functions are frequently used to account for the nonlinear response

of a reference device and/or to improve the visual uniformity of a colour space.

Note 2 to entry: Generally, colour component transfer functions will be nonlinear functions such as a power-law

(i.e. “gamma”) function or a logarithmic function. However, in some cases a linear colour component transfer

function may be used.
[SOURCE: ISO 22028-1:2004, 3.6, modified — Abbreviated term has been added]
3.4
colour gamut

solid in a colour space, consisting of all those colours that are: present in a specific scene, artwork,

photograph, photomechanical or other reproduction; or capable of being created using a particular

output device and/or medium
[SOURCE: ISO 22028-1:2004, 3.8]
3.5
colour rendering

mapping of image data representing the colour-space coordinates of the elements of a scene to output-

referred image data representing the colour-space coordinates of the elements of a reproduction

Note 1 to entry: Colour rendering generally consists of one or more of the following: compensating for differences

in the input and output viewing conditions, tone scale and gamut mapping to map the scene colours onto the

dynamic range and colour gamut of the reproduction, and applying preference adjustments.

[SOURCE: ISO 22028-1:2004, 3.11]
3.6
colour sequence
order in which the colours are stored in an image data file
3.7
orientation

origin and direction of the first line of data, with respect to the image content as viewed by the end user

Note 1 to entry: The codes used to specify orientation are contained in ISO 12639.

3.8
output-referred image state

image state associated with image data that represents the colour-space coordinates of the elements of

an image that has undergone colour rendering appropriate for a specified real or virtual output device

and viewing conditions

Note 1 to entry: When the phrase “output-referred” is used as a qualifier to an object, it implies that the object is

in an output-referred image state. For example, output-referred image data are image data in an output-referred

image state.
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ISO 12640-5:2013(E)

Note 2 to entry: Output-referred image data are referred to the specified output device and viewing conditions. A

single scene can be colour-rendered to a variety of output-referred representations depending on the anticipated

output viewing conditions, media limitations, and/or artistic intents.

Note 3 to entry: Output-referred image data may become the starting point for a subsequent reproduction process.

For example, sRGB output-referred image data are frequently considered to be the starting point for the colour

re-rendering performed by a printer designed to receive sRGB image data.
[SOURCE: ISO 22028-1:2004, 3.33]
3.9
pixel
smallest discrete picture element in a digital image file
3.10
pixel interleaved

colour data organized such that the RGB colour space values for one pixel are followed by the same

sequence of colour values for the next pixel

Note 1 to entry: The specific order of colour components is determined by the ColourSequence tag as defined in

ISO 12639. Other forms of colour data interleaving are line and plane.
3.11
scene

spectral radiances of a view of the natural world as measured from a specified vantage point in space

and at a specified time

Note 1 to entry: A scene may correspond to an actual view of the natural world or to a computer-generated virtual

scene simulating such a view.
[SOURCE: ISO 22028-1:2004, 3.35]
3.12
scene-referred image state

image state associated with image data that represents estimates of the colour-space coordinates of the

elements of a scene

Note 1 to entry: When the phrase “scene-referred” is used as a qualifier to an object, it implies that the object in

a scene-referred image state. For example, scene-referred image data are image data in a scene-referred image

state.

Note 2 to entry: Scene-referred image data can be determined from raw digital still camera (DSC) image data

before colour rendering is performed. Generally, DSCs do not write scene-referred image data in image files, but

some may do so in a special mode intended for this purpose. Typically, DSCs write standard output-referred image

data where colour rendering has already been performed.

Note 3 to entry: Scene-referred image data typically represent relative scene colorimetry estimates. Absolute scene

colorimetry estimates may be calculated using a scaling factor. The scaling factor can be derived from additional

information such as the image OECF, Fnumber or ApertureValue, and ExposureTime or ShutterSpeedValve tags.

Note 4 to entry: Scene-referred image data may contain inaccuracies due to the dynamic range limitations of the

capture device, noise from various sources, quantization, optical blurring and flare that are not corrected for,

and colour analysis errors due to capture device metamerism. In some cases, these sources of inaccuracy can be

significant.

Note 5 to entry: The transformation from raw DSC image to scene-referred image data depends on the relative

adopted whites selected for the scene and the colour space used to encode the image data. If the chosen scene

adopted white is inappropriate, additional errors will be introduced into the scene-referred image data. These

errors may be correctable if the transform used to produce the scene-referred image data is known, and the

colour encoding used for the incorrect scene-referred image data has adequate precision and dynamic range.

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ISO 12640-5:2013(E)

Note 6 to entry: The scene may correspond to an actual view of the natural world, or may be a computer-

generated virtual scene simulating such a view. It may also correspond to a modified scene determined by

applying modifications to an original scene to produce a different desired scene. Any such modifications should

leave the image in a scene-referred image state, and should be done in the context of an expected colour rendering

transform.
[SOURCE: ISO 22028-1:2004, 3.36]
4 Data description
4.1 General

This part of ISO 12640 consists of 47 image data files and specifications of the content of these files

and their use as provided in this part of ISO 12640. The image file names are listed in Table 1, Table 2

and Table 3. The colour image data are encoded in RIMM RGB as specified in ISO/TS 22028-3, using

16 bits/channel and 48 bits/pixel. The image characteristics of these data are described in 4.5 and 4.6,

and the electronic data structure in Clause 5.
4.2 Data set definition

The set of standard colour image data consists of 44 natural images, captured using digital still cameras,

and three synthetic images. The primary set of natural images are identified as NP01 to NP27 and the

secondary set as NS01 to NS17, respectively. Each of them also has a descriptive name derived from the

picture content (e.g. “Falls”). The synthetic images are identified as S1, S2 and S3.

The label “ISO 12640-5 RIMM” is inserted in each image. The coordinates of the text insert

...

INTERNATIONAL ISO
STANDARD 12640-5
First edition
2013-12-15
Graphic technology — Prepress digital
data exchange —
Part 5:
Scene-referred standard colour image
data (RIMM/SCID)
Technologie graphique —Échange de données numériques de
préimpression —
Partie 5: Données d'image standard en couleurs montrées en référence
par scène (RIMM/SCID)
Reference number
ISO 12640-5:2013(E)
ISO 2013
---------------------- Page: 1 ----------------------
ISO 12640-5:2013(E)
This DVD contains:

1) the publication ISO 12640-5:2013 in portable document format (PDF), which can be viewed using

Adobe® Acrobat® Reader;

2) image files NP01RGB.tif to NP27RGB.tif and NS01RGB.tif to NS17RGB.tif, which correspond to the

natural images described in Tables 1 and 2 and depicted in Figure 2;

3) image files S1RGB.tif to S3RGB.tif, which correspond to the synthetic images described in Table 3

and depicted in Figure 3.
Adobe and Acrobat are trademarks of Adobe Systems Incorporated.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

All rights reserved. Unless required for installation or otherwise specified, no part of this DVD may be reproduced, stored in a retrieval

system or transmitted in any form or by any means without prior permission from ISO. Requests for permission to reproduce this product

should be addressed to
ISO copyright office  Case postale 56  CH-1211 Geneva 20  Switzerland
Internet copyright@iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
Published in Switzerland
ii © ISO 2013 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 12640-5:2013(E)
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