ISO/TR 20791-1:2020
(Main)Photography — Photographic reflection prints — Part 1: Evaluation methods of image quality
Photography — Photographic reflection prints — Part 1: Evaluation methods of image quality
This document provides information and examples of measurement methods for evaluating the image quality of digital photographic reflection prints, including prints produced by ink jet, thermal dye transfer, electrophotography and silver halide (chromogenic) technologies. These measurement methods are intended especially to be applicable to small prints with a size of available picture area ranging from 35 mm × 45 mm to 360 mm × 450 mm, a popular and basic application of photographic print technology. NOTE The definition of "digital print" here is print made directly from digital data when there is no intermediate image carrier, or when the image carrier is refreshed for each impression, and thus each impression can be different in content if desired.
Photographie — Tirages photographiques par réflexion — Partie 1: Méthodes d'évaluation de la qualité de l'image
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 20791-1
First edition
2020-08
Photography — Photographic
reflection prints —
Part 1:
Evaluation methods of image quality
Photographie — Tirages photographiques par réflexion —
Partie 1: Méthodes d'évaluation de la qualité de l'image
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Terms . 1
3.2 Abbreviations . 3
4 Overview of the photographic print image quality . 3
4.1 General . 3
4.2 Density and colour . 4
4.3 Uniformity . 4
4.4 Tone . 4
4.5 Detail reproduction . 4
4.6 Glossiness . 4
4.7 Others . 4
5 Density . 5
6 Colour . 5
7 Uniformity . 7
7.1 General . 7
7.2 Micro uniformity . 8
7.2.1 Granularity . 8
7.2.2 Graininess . 8
7.3 Semi-micro uniformity .10
7.4 Macro uniformity .10
8 Tone .12
8.1 Tone reproduction .12
8.2 Capacity for tone reproduction .12
9 Detail reproduction .13
9.1 General .13
9.2 Resolution measured with patterns of fine lines.13
9.3 Resolution measured with contrast-resolution test target .15
10 Glossiness .16
10.1 General .16
10.2 Specular gloss .16
10.3 Sharpness of reflected light (Image clarity and distinctness of image) .17
Bibliography .20
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
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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).
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
A list of all parts in the ISO 20791 series can be found on the ISO website.
iv © ISO 2020 – All rights reserved
Introduction
Image quality of photographic prints is not based on any single feature but instead involves several
factors. There are so-called “five major properties” for representing photographic image quality, and
each one is essential: (1) density; (2) colour; (3) uniformity; (4) tone and (5) detail reproduction.
Glossiness represents another important factor. It affects the observer’s perception since it relates to
the light specularly reflected from prints. Though the specularly reflected light contains no information
from the printed image, it affects the observer’s perception. Furthermore, sharpness of the shape of
reflected light sources also affects the perception.
Several standards for image quality measurement have been documented by ISO/TC 42. Standards
intended for analogue prints fail to properly address the effect of half tone dots, which required to
produce inkjet and electrophotographic prints.
In recent years, the field of imaging science and technology has witnessed the investigation of
measurement methods for digital prints. In addition, standards have been developed by ISO/IEC JTC 1/
SC 28 and ISO/TC 130. Some of these standards cannot be applied broadly to photographic prints
because they focus on a specific technical or industrial field. However, the rest of these standards
handle common aspects and can be applied to photographic prints with or without modifying the
standard. This document provides information about the measurement methods for image quality
that are applicable to photographic prints, including digital prints produced using a range of printing
technologies.
ISO/TC 42 plans to develop test targets for image quality measurements on small size photographic
prints. This document provides methods which can be applied for the measurements.
TECHNICAL REPORT ISO/TR 20791-1:2020(E)
Photography — Photographic reflection prints —
Part 1:
Evaluation methods of image quality
1 Scope
This document provides information and examples of measurement methods for evaluating the
image quality of digital photographic reflection prints, including prints produced by ink jet, thermal
dye transfer, electrophotography and silver halide (chromogenic) technologies. These measurement
methods are intended especially to be applicable to small prints with a size of available picture area
ranging from 35 mm × 45 mm to 360 mm × 450 mm, a popular and basic application of photographic
print technology.
NOTE The definition of “digital print” here is print made directly from digital data when there is no
intermediate image carrier, or when the image carrier is refreshed for each impression, and thus each impression
can be different in content if desired.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 Terms
3.1.1
reflectance factor
ratio of the reflected flux as measured to the reflected flux under the same geometrical and spectral
conditions for an ideal 100 % diffuse reflecting surface
[SOURCE: ISO/IEC 24790:2017, 3.30]
3.1.2
spots per inch
spi
spots per 25,4 mm
[SOURCE: ISO/IEC 24790:2017, 3.34]
3.1.3
visual transfer function
VTF
function used to represent human visual characteristics when dividing the system into parts and
evaluating it as a superposition of transfer functions in the spatial frequency domain
3.1.4
mura
non-uniformity in the image that should be of uniform density or uniform colour
Note 1 to entry: Mura defects are larger than graininess or mottle, and it generally has ambiguous boundaries.
3.1
...
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