ISO 26431-1:2008

INTERNATIONAL ISO
STANDARD 26431-1
First edition
2008-09-01
Digital cinema (D-cinema) quality —
Part 1:
Screen luminance level, chromaticity
and uniformity
Qualité du cinéma numérique (cinéma D) —
Partie 1: Niveau de luminance d'écran, chromaticité et uniformité

Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 26431-1 was prepared by the Society of Motion Picture and Television Engineers (as
SMPTE 431-1-2006) and was adopted, under a special “fast-track procedure”, by Technical Committee
ISO/TC 36, Cinematography, in parallel with its approval by the ISO member bodies.
ISO 26431 consists of the following parts, under the general title Digital cinema (D-cinema) quality:
⎯ Part 1: Screen luminance level, chromaticity and uniformity

Introduction
This International Standard comprises SMPTE 431-1-2006 and the following informative notes.
⎯ Informative reference: The French national standard NF S27-100, Cinematography — Electronic
projection rooms of digital cinema type, provides additional regional information.
⎯ Stray light and contrast (see Clause A.7): The reader is encouraged to review national standards and
recommendations.
iv © ISO 2008 – All rights reserved

SMPTE 431-1-2006
SMPTE STANDARD
for D-Cinema Quality —
Screen Luminance Level,
Chromaticity and Uniformity
Page 1 of 5 pages
1 Scope
This standard specifies the absolute luminance level, white point chromaticity, and luminance uniformity of the
reflected screen light for the presentation of motion pictures by projectors with digital light engines in review
rooms and commercial cinemas. It is the purpose of this specification to achieve the tone scale and contrast
in the projected image that will correspond to that intended during the mastering process.

2 Normative reference
The following standards contain provisions which, through reference in this text, constitute provisions of this
standard. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreement based on this standard are encouraged to investigate the possibility of applying the
most recent edition of the standards indicated below.

ISO 10527:2007, CIE standard colorimetric observers

3 Performance classes
It should be recognized that different applications within the industry have varying requirements for
tolerances, or the precision of the target specifications attained in any particular installation. For example,
greater precision may be required for a system in a mastering suite than in a commercial cinema theatre. In
order to simplify communication, two levels or classes of precision are defined herein as follows:

Review Room intended as the highest practical precision, for the most critical colorimetry
applications, recommended for the mastering activities of color timing and
color matching.
Theater   intended as the minimum level for commercial cinema presentations.

Performance criteria for each class are defined in section 5.

4 Measurement criteria
4.1 Projector conditions
Measurements shall be made with the projector in normal operation, with its lens(es) set at optimal focus
position, set for the format covering the largest area of the screen, and a 100% white signal being displayed
on the screen (either the entire screen or as a minimum the five zones consisting of the screen center and
four corner locations defined in section 4.2). The 100% white signal is defined as the digital code values
assigned to the maximum color-neutral white level allowed in the input signal standard of interest.
MOTION PICTURE AND TELEVISION ENGINEERS
April 18, 2006
3 Barker Avenue, White Plains, NY 10601
(914) 761-1100
SMPTE 431-1-2006
4.2 Measurement locations on the screen

Measurements of light levels shall be taken at screen locations consisting of the geometric center of the
screen and the four sides in theaters, and those measurements with the addition of the four corners in review
rooms. The side and corner locations are inset 5% ± 1% of the screen width from both of the adjacent screen
edges.
4.3 Measurement locations in the auditorium

All screen measurements shall be performed at the center of the seating row closest to the geometric center
of the seating area. All readings shall be taken at a height of approximately 1.1 m (43 in) above the floor to
simulate the eye height of an audience member.

4.4 Photometer type
Screen luminance shall be measured with a spot photometer having the spectral luminance response of the
standard observer (photopic vision), as defined in ISO 10527:2007. The acceptance angle of the photometer
shall be 2° or less. The photometer shall have an accuracy of ± 0.5 cd/m² (± 0.2 fL) or better. The photometer
response to luminance variation over time shall be to properly integrate any such variation occurring at
frequencies at or above 24 Hz and display the arithmetic mean value.

4.5 Spectroradiometer type
Screen chromaticity shall be measured with a spot spectroradiometer w
...