Graphic technology — Displays for colour proofing — Characteristics

ISO 12646:2015 specifies requirements for two conformance levels for the characteristics of displays to be used for soft proofing of colour images. Included are requirements for uniformity and variations of electro-optical properties with viewing direction for different driving signals.

Technologie graphique — Affichages pour la réalisation d'épreuves en couleur — Caractéristiques

Grafična tehnologija - Zasloni za barvno preskušanje - Značilnosti

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zaslonov za mehko preskušane barvnih slik. Vključene so zahteve za enotnost in
različice elektro-optičnih lastnosti s smerjo ogleda za različne vozne signale.

General Information

Status
Published
Publication Date
18-Jun-2015
Current Stage
9093 - International Standard confirmed
Completion Date
02-Aug-2022

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INTERNATIONAL ISO
STANDARD 12646
Third edition
2015-07-15
Graphic technology — Displays for
colour proofing — Characteristics
Technologie graphique — Affichages pour la réalisation d’épreuves en
couleur — Caractéristiques
Reference number
ISO 12646:2015(E)
ISO 2015
---------------------- Page: 1 ----------------------
ISO 12646:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, 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 2015 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 12646:2015(E)
Contents Page

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

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

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

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

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

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

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

4.2 Uniformity of luminance and chromaticity .................................................................................................................... 3

4.2.1 General...................................................................................................................................................................................... 3

4.2.2 Evaluation of tone uniformity ............................................................................................................................... 3

4.2.3 Tonality evaluation (uniformity) ....................................................................................................................... 3

4.3 Viewing cone characteristics ...................................................................................................................................................... 3

4.4 Reflective characteristics ............................................................................................................................................................... 4

5 Test methods ............................................................................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Preparation and display set-up ................................................................................................................................................. 5

5.3 Viewing angle dependent tonality evaluation (“∆Gamma”) ............................................................................ 5

5.4 Measurement conditions ......... ....................................................................................................................................................... 6

5.4.1 Photometric and colorimetric measurements ....................................................................................... 6

5.4.2 Measurements as a function of viewing direction .............................................................................. 8

Bibliography .............................................................................................................................................................................................................................11

© ISO 2015 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 12646:2015(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 third edition cancels and replaces the second edition (ISO 12646:2008), which has been technically

revised to improve the compatibility with the requirements of soft proofing defined in ISO 14861.

iv © ISO 2015 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 12646:2015(E)
Introduction

The ability to match colour images displayed on colour displays to the images produced when the same

digital file is rendered by proofing and printing systems (commonly referred to as “soft” proofing) is

increasingly expected in graphic arts. Obtaining such a match is not simple and to be fully accurate

requires careful control of many aspects of the process. The primary purpose of this International

Standard is to make recommendations with respect to the soft proof displays requirements. If these

are met, it is then possible for a soft proofing system such as defined in ISO 14861 to accurately colour

match to the hard copy proof. Hence, this International Standard is intended for display manufacturers

in order to qualify their display for use in graphic arts proofing systems.

The appearance of a colour image on a colour display is influenced by many physical factors other than

controlled ambient viewing conditions. Among the most important of these are uniformity, size and

resolution (in order to permit rendition of the proof at close to its normal size and with the finest detail

visible on the hard copy at normal viewing distances), variation of electro-optical properties with

viewing direction, freedom from flicker and glare (specular reflections with distinct images), the opto-

electronic calibration of the display, and the settings of its display driver software. In this regard, to be

acceptable in a proofing system that provides a reasonable level of image quality, the display needs to

also exhibit these properties at an acceptable quality.

Note that even for displays of the highest quality, the appearance of the displayed image will be limited

by the accuracy of the colour transformation used for converting the digital file from its encoded colour

space to that required for display purposes.

This International Standard specifies requirements for displays to be used in soft proofing systems

defined by ISO 14861. ISO 14861 primarily focuses on applications where the displayed image will be

compared to a hard copy in an adjacent viewing cabinet or where the viewing cabinet intentionally

contains the display. Furthermore, in order to address the different needs for the soft proofing use cases,

two different conformance levels (class A and class B) will be defined in this International Standard.

However, in some practical situations, the image on the screen is evaluated in the absence of a hard

copy. This International Standard might be used as reference, but this is not required. Users of this

International Standard will also benefit from CIE Publication 122 which provides an overview of the

relationship between digital and colorimetric data. Those unfamiliar with the evaluation of displays

will also find it helpful to read IEC 61223-2-5 which contains much useful detailed information about

evaluation and testing of image display devices.
© ISO 2015 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 12646:2015(E)
Graphic technology — Displays for colour proofing —
Characteristics
1 Scope

This International Standard specifies requirements for two conformance levels for the characteristics

of displays to be used for soft proofing of colour images. Included are requirements for uniformity and

variations of electro-optical properties with viewing direction for different driving signals.

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 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
calibration

set of operations that establish, under specified conditions, the relationship between values of quantities

indicated by a measuring instrument or measuring system or values represented by a material measure

of a reference material and the corresponding values realized by standards
[SOURCE: ISO International Vocabulary of Basic and General Terms in Metrology]

Note 1 to entry: However, in typical graphic arts, use cases calibration is understood as an active process where a

display or a printer is adjusted such that it produces the defined aim values.
3.2
colorimeter

instrument for measuring colour values such as the tristimulus values of a colour stimulus

[SOURCE: ISO 12637-2:2008, 2.18]
3.3
design viewing direction
DVD

direction for which specific electro-optical characteristics of the display have been optimized

Note 1 to entry: Examples of important electro-optical characteristics are maximum luminance and maximum

contrast in definite direction.
3.4
gamma

best-fit parameter which relates the display normalized output luminance to a normalized input digital value

presented to the display system including its hardware and software components as given in Formula (1):

LS= +O
© ISO 2015 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 12646:2015(E)
where
L is the normalized output luminance;
S is the normalized input digital value;
O is the offset.
3.5
ON-state
condition in which the display is switched on

Note 1 to entry: This definition is important for light-valve-like displays which might emit a significant light

intensity even when displaying the darkest image (R = G = B = 0) in the ON-state.

3.6
spectrophotometer

instrument for measuring the reflectance or transmittance of light (or other radiation) by an object at

one or more wavelengths in the spectrum
[SOURCE: ISO 105-A08:2001, 2.24]
3.7
viewing cone

conical space originating at the display surface that includes all viewing directions with a specified

angle of inclination, θ (3.8)
3.8
viewing angle
angle between the normal to the display and the design viewing direction (3.3)
4 Requirements
4.1 General

All display tests should be performed for a display calibrated to a luminance of 160 cd/m and a

chromaticity corresponding to a D50 (x = 0,3 457 and y = 0,3 585) illuminant with a 2° observer at

a gamma of 2,2. The display shall display a ”white” image consisting of the maximum value in each

channel, red, green, and blue (255 for 8-bit). It shall be reported if other calibration aims were used.

NOTE 1 This calibration condition is typical of the conditions used in the graphic arts industry and ensures

that the results of different tested displays can be compared because uniformity can be dependent to some extent

on the chosen gamma, luminance, and white point settings.

If a display to be tested will be used solely in a specific soft proofing system where no display calibration

is used, but only the state of the display is characterized, the calibration can be omitted. The luminance,

the white point chromaticity (as expressed in CIExy units), and tone reproduction curve (as expressed

by a single gamma value or as a set of tabulated values) shall be reported.

The display shall be tested in a stable condition. In order to establish the individual stabilization time,

each display to be tested shall be operated in the calibration mode for 12 h in a room with controlled

temperature conditions. The room temperature shall not change more than ±0,5 °C and shall be in the

range of 18 °C to 28 °C.

The stabilization time (warm up time) is achieved when the luminance change is less than 2 % (compared to

the average of the measurements of the last 9 h of the 12 h period) and the white point is within ±0,005 for

CIE Δx, Δy of the calibrated conditions. If the display will not achieve stable conditions, it shall not be used.

2 © ISO 2015 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 12646:2015(E)

The warm up behaviour of a display shall be reported with a graph of luminance and CIE Δx, Δy in

measured values and in percentage compared to the average of the last 9 h of the 12 h period.

NOTE 2 When using viewing condition P2, according to ISO 3664, a luminance of 160 cd/m correlates with an

illuminance of 500 lux illuminating a perfect reflecting diffusor.
4.2 Uniformity of luminance and chromaticity
4.2.1 General

The uniformity of a soft proofing system is vital and shall be checked for solid colours and for tonality

(gradation) changes of the screen. If the informative requirements of 4.2.2. or 4.2.3 are not met, this

shall be reported. Therefore, the following method is normatively required in ISO 14861. However, since

there are soft proofing solutions that are able to perform a spatial resolved uniformity correction, this

International Standard makes the uniformity assessment informative.

It shall be reported and if hardware based, look up table display corrections are turned on (if present).

4.2.2 Evaluation of tone uniformity

The CIELAB values of a uniform 5 × 5 grid are calculated using the measurement of the centre patch at

maximum driving as the reference white illuminant. Note that this method may result in some CIEL*

values being greater than 100. 24 readings are compared with the centre colour for three different driving

levels, namely white, at the maximum driving level (R = G = B = 255 for 8-bit displays), grey at about half

maximum driving level (R = G = B = 127 for 8-bit displays), and dark grey at about one fourth of maximum

driving level (R = G = B = 63 for 8-bit displays) by means of the DE00 colour difference formulae. For the

white and the grey driving levels, the DE00 colour differences should be equal or less than four.

4.2.3 Tonality evaluation (uniformity)

Utilizing luminance (cd/m ) measurements of grey at half maximum driving level (R = G = B = 127 for

8-bit displays) and white at max driving level (R = G = B = 255 for 8-bit displays) the grey/white ratio

should be calculated for the 25 regions. For the non-central regions, new ratios, T , with i = {1,..,24} should

be computed by dividing the individual grey/white ratios, R , with i = {1,...,24} by the grey/white ratio

of the centre, R , subtracting one and calculate the absolute value of the number. This measure of the

deviation from uniform tonality should be less than 10 %, i.e. max (T ), i = {1,..,24} should be less than 0,10.

Ta=−bs RR/,1 i=1,...,24 (1)
() ()
ii c

The uniformity of tonality, determined as max (T ), with i = {1,..,24}, should be less than 0,1.

4.3 Viewing cone characteristics

The instrumentation setup and measurement geometry for viewing cone measurements shall be as

defined in 5.4.2.
Based on the viewing cone which is visible for a
...

SLOVENSKI STANDARD
SIST ISO 12646:2016
01-maj-2016
1DGRPHãþD
SIST ISO 12646:2010
SIST ISO 12646:2010/Dod 1:2014
*UDILþQDWHKQRORJLMD=DVORQL]DEDUYQRSUHVNXãDQMH=QDþLOQRVWL
Graphic technology - Displays for colour proofing - Characteristics
Technologie graphique - Affichages pour la réalisation d'épreuves en couleur -
Caractéristiques
Ta slovenski standard je istoveten z: ISO 12646:2015
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
37.100.10 Reprodukcijska oprema Reproduction equipment
SIST ISO 12646:2016 en

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

---------------------- Page: 1 ----------------------
SIST ISO 12646:2016
---------------------- Page: 2 ----------------------
SIST ISO 12646:2016
INTERNATIONAL ISO
STANDARD 12646
Third edition
2015-07-15
Graphic technology — Displays for
colour proofing — Characteristics
Technologie graphique — Affichages pour la réalisation d’épreuves en
couleur — Caractéristiques
Reference number
ISO 12646:2015(E)
ISO 2015
---------------------- Page: 3 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, 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 2015 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(E)
Contents Page

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

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

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

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

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

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

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

4.2 Uniformity of luminance and chromaticity .................................................................................................................... 3

4.2.1 General...................................................................................................................................................................................... 3

4.2.2 Evaluation of tone uniformity ............................................................................................................................... 3

4.2.3 Tonality evaluation (uniformity) ....................................................................................................................... 3

4.3 Viewing cone characteristics ...................................................................................................................................................... 3

4.4 Reflective characteristics ............................................................................................................................................................... 4

5 Test methods ............................................................................................................................................................................................................. 5

5.1 General ........................................................................................................................................................................................................... 5

5.2 Preparation and display set-up ................................................................................................................................................. 5

5.3 Viewing angle dependent tonality evaluation (“∆Gamma”) ............................................................................ 5

5.4 Measurement conditions ......... ....................................................................................................................................................... 6

5.4.1 Photometric and colorimetric measurements ....................................................................................... 6

5.4.2 Measurements as a function of viewing direction .............................................................................. 8

Bibliography .............................................................................................................................................................................................................................11

© ISO 2015 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(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 third edition cancels and replaces the second edition (ISO 12646:2008), which has been technically

revised to improve the compatibility with the requirements of soft proofing defined in ISO 14861.

iv © ISO 2015 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(E)
Introduction

The ability to match colour images displayed on colour displays to the images produced when the same

digital file is rendered by proofing and printing systems (commonly referred to as “soft” proofing) is

increasingly expected in graphic arts. Obtaining such a match is not simple and to be fully accurate

requires careful control of many aspects of the process. The primary purpose of this International

Standard is to make recommendations with respect to the soft proof displays requirements. If these

are met, it is then possible for a soft proofing system such as defined in ISO 14861 to accurately colour

match to the hard copy proof. Hence, this International Standard is intended for display manufacturers

in order to qualify their display for use in graphic arts proofing systems.

The appearance of a colour image on a colour display is influenced by many physical factors other than

controlled ambient viewing conditions. Among the most important of these are uniformity, size and

resolution (in order to permit rendition of the proof at close to its normal size and with the finest detail

visible on the hard copy at normal viewing distances), variation of electro-optical properties with

viewing direction, freedom from flicker and glare (specular reflections with distinct images), the opto-

electronic calibration of the display, and the settings of its display driver software. In this regard, to be

acceptable in a proofing system that provides a reasonable level of image quality, the display needs to

also exhibit these properties at an acceptable quality.

Note that even for displays of the highest quality, the appearance of the displayed image will be limited

by the accuracy of the colour transformation used for converting the digital file from its encoded colour

space to that required for display purposes.

This International Standard specifies requirements for displays to be used in soft proofing systems

defined by ISO 14861. ISO 14861 primarily focuses on applications where the displayed image will be

compared to a hard copy in an adjacent viewing cabinet or where the viewing cabinet intentionally

contains the display. Furthermore, in order to address the different needs for the soft proofing use cases,

two different conformance levels (class A and class B) will be defined in this International Standard.

However, in some practical situations, the image on the screen is evaluated in the absence of a hard

copy. This International Standard might be used as reference, but this is not required. Users of this

International Standard will also benefit from CIE Publication 122 which provides an overview of the

relationship between digital and colorimetric data. Those unfamiliar with the evaluation of displays

will also find it helpful to read IEC 61223-2-5 which contains much useful detailed information about

evaluation and testing of image display devices.
© ISO 2015 – All rights reserved v
---------------------- Page: 7 ----------------------
SIST ISO 12646:2016
---------------------- Page: 8 ----------------------
SIST ISO 12646:2016
INTERNATIONAL STANDARD ISO 12646:2015(E)
Graphic technology — Displays for colour proofing —
Characteristics
1 Scope

This International Standard specifies requirements for two conformance levels for the characteristics

of displays to be used for soft proofing of colour images. Included are requirements for uniformity and

variations of electro-optical properties with viewing direction for different driving signals.

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 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
calibration

set of operations that establish, under specified conditions, the relationship between values of quantities

indicated by a measuring instrument or measuring system or values represented by a material measure

of a reference material and the corresponding values realized by standards
[SOURCE: ISO International Vocabulary of Basic and General Terms in Metrology]

Note 1 to entry: However, in typical graphic arts, use cases calibration is understood as an active process where a

display or a printer is adjusted such that it produces the defined aim values.
3.2
colorimeter

instrument for measuring colour values such as the tristimulus values of a colour stimulus

[SOURCE: ISO 12637-2:2008, 2.18]
3.3
design viewing direction
DVD

direction for which specific electro-optical characteristics of the display have been optimized

Note 1 to entry: Examples of important electro-optical characteristics are maximum luminance and maximum

contrast in definite direction.
3.4
gamma

best-fit parameter which relates the display normalized output luminance to a normalized input digital value

presented to the display system including its hardware and software components as given in Formula (1):

LS= +O
© ISO 2015 – All rights reserved 1
---------------------- Page: 9 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(E)
where
L is the normalized output luminance;
S is the normalized input digital value;
O is the offset.
3.5
ON-state
condition in which the display is switched on

Note 1 to entry: This definition is important for light-valve-like displays which might emit a significant light

intensity even when displaying the darkest image (R = G = B = 0) in the ON-state.

3.6
spectrophotometer

instrument for measuring the reflectance or transmittance of light (or other radiation) by an object at

one or more wavelengths in the spectrum
[SOURCE: ISO 105-A08:2001, 2.24]
3.7
viewing cone

conical space originating at the display surface that includes all viewing directions with a specified

angle of inclination, θ (3.8)
3.8
viewing angle
angle between the normal to the display and the design viewing direction (3.3)
4 Requirements
4.1 General

All display tests should be performed for a display calibrated to a luminance of 160 cd/m and a

chromaticity corresponding to a D50 (x = 0,3 457 and y = 0,3 585) illuminant with a 2° observer at

a gamma of 2,2. The display shall display a ”white” image consisting of the maximum value in each

channel, red, green, and blue (255 for 8-bit). It shall be reported if other calibration aims were used.

NOTE 1 This calibration condition is typical of the conditions used in the graphic arts industry and ensures

that the results of different tested displays can be compared because uniformity can be dependent to some extent

on the chosen gamma, luminance, and white point settings.

If a display to be tested will be used solely in a specific soft proofing system where no display calibration

is used, but only the state of the display is characterized, the calibration can be omitted. The luminance,

the white point chromaticity (as expressed in CIExy units), and tone reproduction curve (as expressed

by a single gamma value or as a set of tabulated values) shall be reported.

The display shall be tested in a stable condition. In order to establish the individual stabilization time,

each display to be tested shall be operated in the calibration mode for 12 h in a room with controlled

temperature conditions. The room temperature shall not change more than ±0,5 °C and shall be in the

range of 18 °C to 28 °C.

The stabilization time (warm up time) is achieved when the luminance change is less than 2 % (compared to

the average of the measurements of the last 9 h of the 12 h period) and the white point is within ±0,005 for

CIE Δx, Δy of the calibrated conditions. If the display will not achieve stable conditions, it shall not be used.

2 © ISO 2015 – All rights reserved
---------------------- Page: 10 ----------------------
SIST ISO 12646:2016
ISO 12646:2015(E)

The warm up behaviour of a display shall be reported with a graph of luminance and CIE Δx, Δy in

measured values and in percentage compared to the average of the last 9 h of the 12 h period.

NOTE 2 When using viewing condition P2, according to ISO 3664, a luminance of 160 cd/m correlates with an

illuminance of 500 lux illuminating a perfect reflecting diffusor.
4.2 Uniformity of luminance and chromaticity
4.2.1 General

The uniformity of a soft proofing system is vital and shall be checked for solid colours and for tonality

(gradation) changes of the screen. If the informative requirements of 4.2.2. or 4.2.3 are not met, this

shall be reported. Therefore, the following method is normatively required in ISO 14861. However, since

there are soft proofing solutions that are able to perform a spatial resolved uniformity correction, this

International Standard makes the uniformity assessment informative.

It shall be reported and if hardware based, look up table display corrections are turned on (if present).

4.2.2 Evaluation of tone uniformity

The CIELAB values of a uniform 5 × 5 grid are calculated using the measurement of the centre patch at

maximum driving as the reference white illuminant. Note that this method may result in some CIEL*

values being greater than 100. 24 readings are compared with the centre colour for three different driving

levels, namely white, at the maximum driving level (R = G = B = 255 for 8-bit displays), grey at about half

maximum driving level (R = G = B = 127 for 8-bit displays), and dark grey at about one fourth of maximum

driving level (R = G = B = 63 for 8-bit displays) by means of the DE00 colour difference formulae. For the

white and the grey driving levels, the DE00 colour differences should be equal or less than four.

4.2.3 Tonality evaluation (uniformity)

Utilizing luminance (cd/m ) measurements of grey at half maximum driving level (R = G = B = 127 for

8-bit displays) and white at max driving level (R = G = B = 255 for 8-bit displays) the grey/white ratio

should be calculated for the 25 regions. For the non-central regions, new ratios, T , with i = {1,..,24} should

be computed by dividing the individual grey/white ratios, R , with i = {1,...,24} by the grey/white ratio

of the centre, R , subtracting one and calculate t
...

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