Automatic identification and data capture techniques — Bar code print quality test specification — Evolution of the grading and measurement of linear symbols in ISO/IEC 15416

This document explains the changes incorporated in ISO/IEC 15416:2016 compared to ISO/IEC 15416:2000 and highlights the impact of these changes for the users' benefit.

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Status
Published
Publication Date
10-May-2022
Current Stage
2020 - Working draft (WD) study initiated
Start Date
19-Oct-2018
Completion Date
19-Oct-2018
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ISO/IEC TR 24244:2022 - Automatic identification and data capture techniques — Bar code print quality test specification — Evolution of the grading and measurement of linear symbols in ISO/IEC 15416 Released:5/11/2022
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TECHNICAL ISO/IEC TR
REPORT 24244
First edition
2022-05
Automatic identification and data
capture techniques — Bar code print
quality test specification — Evolution
of the grading and measurement of
linear symbols in ISO/IEC 15416
Reference number
ISO/IEC TR 24244:2022(E)
© ISO/IEC 2022
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ISO/IEC TR 24244:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
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Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO/IEC 2022 – All rights reserved
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ISO/IEC TR 24244:2022(E)
Contents Page

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

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

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

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

4 Historical background leading to ISO/IEC 15416:2016 .............................................................................................. 1

5 Summary of changes introduced in ISO/IEC 15416:2016 ......................................................................................... 2

5.1 R eview of measurements and grades ................................................................................................................................ 2

5.2 Change to number of grade levels ......................................................................................................................................... 2

5.3 Change to measurement of defect ......................................................................................................................................... 2

6 Continuous grading ........................................................................................................................................................................................... 3

7 Changes to defect measurement .........................................................................................................................................................4

8 Impact of continuous grading on final grades and application standards ............................................4

8.1 General ........................................................................................................................................................................................................... 4

8.2 Grading situations ............................................................................................................................................................................... 5

8.2.1 Grades consistently at high end of a grade range ................................................................................. 5

8.2.2 Grades consistently at low end of a grade range ................................... ................................................. 5

8.2.3 Grades consistently at midpoint of a grade range ................................................................................ 5

8.2.4 Grades fluctuating across grade boundary ................................................................................................ 5

8.3 Impact of continuous grading on existing application standards ............................................................ 6

8.3.1 Similar Results at different minimum grade level ............................................................................... 6

8.3.2 Impact to application standards if acceptable minimum grade level is not

changed ....................................................................................................................................................................................... 6

9 Conclusion ................................................................................................................................................................................................................... 8

Bibliography ................................................................................................................................................................................................................................ 9

iii
© ISO/IEC 2022 – All rights reserved
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ISO/IEC TR 24244:2022(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical

activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international

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

work.

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 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 or

www.iec.ch/members_experts/refdocs).

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

of patent rights. ISO and IEC 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) or the IEC

list of patent declarations received (see https://patents.iec.ch).

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

constitute an endorsement.

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

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

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.

This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,

Subcommittee SC 31, Automatic identification and data capture techniques.

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 and

www.iec.ch/national-committees.
© ISO/IEC 2022 – All rights reserved
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TECHNICAL REPORT ISO/IEC TR 24244:2022(E)
Automatic identification and data capture techniques —
Bar code print quality test specification — Evolution of the
grading and measurement of linear symbols in ISO/IEC
15416
1 Scope

This document explains the changes incorporated in ISO/IEC 15416:2016 compared to

ISO/IEC 15416:2000 and highlights the impact of these changes for the users' benefit.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

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

ISO/IEC 15416:2016, Automatic identification and data capture techniques — Bar code print quality test

specification — Linear symbols
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 15416:2016 apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Historical background leading to ISO/IEC 15416:2016

ISO/IEC 15416 was first published in 2000 and has been used in many industries throughout the world.

Based on a method first developed and published by ANSI in 1990 as X3.182-1990, the methodology

for bar code grading has become a foundation of barcode quality in many industries including supply

chain management, retail point of sale, warehousing, shipping and logistics, pharmaceutical labelling

and many others.

Even with the widespread adoption of ISO/IEC 15416 as the basis of bar code quality measurement,

some problems and opportunity for improvement were noticed by many users and members of ISO/

IEC JTC1/SC31/WG1 which is responsible for ISO/IEC 15416. Chief among these was the tendency for

grades to fluctuate under repeated trials. Accordingly, the revision of ISO/IEC 15416 in 2016 introduced

several changes to the grading methodology with the intention of reducing grade variability

Another criticism of ISO/IEC 15416 grading is that scanning/reading technology has improved

significantly since its introduction, resulting in a reduction in the correlation between quality grade

and real-world scanning performance. Accordingly, the revision of ISO/IEC 15416 in 2016 tends to

assign higher grades than before, as is described in this report.

These problems have been largely resolved by the publication of ISO/IEC 15416:2016. This document:

— explains the changes introduced in ISO/IEC 15416:2016;

— explains why these changes were introduced and how they reduce the problems outlined above;

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ISO/IEC TR 24244:2022(E)
— explains the impact of these changes in existing application standards;

— helps new and existing application standards to consider how to respond to these impacts.

5 Summary of changes introduced in ISO/IEC 15416:2016
5.1 R eview of measurements and grades

In the grading method of ISO/IEC 15416, quality parameters are measured and then graded. A measured

value for a parameter is obtained on a nominally continuous scale, typically from 0 to 100. In general,

grade levels are assigned to ranges of measured values. Prior to the 2016 revision, ISO/IEC 15416

defined only five grade levels, namely 0, 1, 2, 3 or 4, with 4 being the highest or best grade and 0 being

the lowest and worst grade. (Historically, these grades correspond to the letter grades used in ANSI

X3.182, namely A, B, C, D and F). For example, for the parameter called Symbol Contrast, any measured

value in the range of 40 through 55 was assigned a grade level of 2 (corresponding to a “C” in ANSI

X3.182).

NOTE The grades 0, 1, 2, 3 and 4 are commonly associated with the ANSI X3.182 grades of F, D, C, B and A and

this relationship is noted here for reference only.
5.2 Change to number of grade levels

The assignment of a range of measured values to a single grade, and the fact that there are only five

grade levels covering five ranges has two significant consequences. The first is that there is a sharp

transition at the boundary of measured value ranges. For example, when symbol contrast is measured

as to be 39 it is graded as 1 but when it is measured as 40 or more it is graded as 2. While there is

no practical difference in quality between 39 and 40 for symbol quality, there is quite a significant

difference in the grades of 1 and 2. Thus the meaning of the grade 1 and 2 is not clear because it is

not possible to know (from the grade alone) whether the measured parameter was near the boundary

between these grade levels.

The other consequence, as can be anticipated from the previous discussion, is that small variations in

the measured values, which are inevitable due to tolerances in any measurement system, can result in

large fluctuations in grade (namely a change in grade of 1 full grade level). This effect is exacerbated

when the bounded range for a grade is small, as it is for defect (range of only 5) and modulation (range

of only 10). The most significant impact from narrow ranges is that measurements are often near

boundaries between grade levels, and thus even normal tolerances are more likely to produce changes

in grade levels.

NOTE The allowed tolerance for defect and symbol contrast is 8 which is significant compared to the size of

the bounded ranges, which in the case of defect is actually smaller than the allowed tolerance which is 8.

To reduce grade variability, the process of assigning grades to the measured parameters was changed

in ISO/IEC 15416:2016, by increasing the number of grade levels from 5 to 41, corresponding to

grade levels represented by decimal number 4,0 down to 0 in steps of 0,1. This can be referred to as

“continuous grading” but in fact is stepwise, albeit with smaller steps than before.

5.3 Change to measurement of defect

Another significant change to ISO/IEC 15416 was to introduce a modification to the measurement of

DEFECT, again to reduce a potential source of grade fluctuation. This modification creates a gradual

change in the defect measurement value for a gradual change in the size of the size of a “peak” or “valley”

in the scan reflectance profile to prevent large grade changes that could occur in the old grading system

when a “peak” or “valley” is very small compared to not present at all.

NOTE The grade for DEFECT also utilizes the continuous grading concept described above, but also has

another change that is specific to calculating the DEFECT measurement value.
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ISO/IEC TR 24244:2022(E)
6 Continuous grading

ISO/IEC 15416:2016 introduced “continuous grading” which assigns grades on a gradual basis rather

than using only five levels. Figure 1 shows the five grade levels for symbol contrast (SC) defined in

ISO/IEC 15416:2000.
Figure 1 — “Staircase” showing values for SC, assigned to integer grade levels

The continuous grading scale is from 0 to 4 (in keeping with the original grade levels) but assigns values

with a step size of 0,1 as shown in Figure 2.

Figure 2 — Continuous grades for symbol contrast, assigned to 41 smaller grade levels

With continuous grading, much smaller ranges of measured values, are assigned to many more grade

levels, providing almost continuous grading. The grading is not completely continuous because of the

rule that the grade shall be rounded to the nearest tenth, but this is practically inconsequential. The

transition from grades 1 to 0 occurs over a small range with a grade of 0 being reached before the

measured value reaches zero.
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ISO/IEC TR 24244:2022(E)
7 Changes to defect measurement

A change to the measurement of defect was also introduced in ISO/IEC 15416:2016. This change is

quite independent of the continuous grading change discussed in this document. For completeness, this

document also describes the change to the defect measurement.

NOTE Even though the change to defect described in this clause is independent of the continuous grading

change, the grade level assignment for defect is also modified to use continuous grading.

A defect is defined as element non-uniformity and is measured by the degree of reflectance variation

within an element (bar or space) as a fraction of the symbol contrast. Because elements begin at the

boundary where its scan reflectance profile (SRP) transitions across a reflectance threshold, the

element non-uniformity is selected only at points represented by a “peak” or a “valley” as illustrated in

Figure 3. Note that point “A” does not represent the maximum reflectance for this element, only point

“B” does.
Key
Global threshold.

Figure 3 — Fragment of a scan reflectance profile showing a peak within a bar element

However, the search for “peaks” and “valleys” can lead to unintended consequences when small

fluctuations in the SRP, especially near the threshold, can be alternately perceived as a “peak” or

“valley” or not seen as one of those. Therefore, ISO/IEC 15416:2016 introduces a formula which

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