1、 Reference number ISO 26431-1:2008(E) ISO 2008INTERNATIONAL STANDARD ISO 26431-1 First edition 2008-09-01 Digital cinema (D-cinema) quality Part 1: Screen luminance level, chromaticity and uniformity Qualit du cinma numrique (cinma D) Partie 1: Niveau de luminance dcran, chromaticit et uniformit ISO
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5、ven below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at th
6、e address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedISO 26431-1:2008(E) ISO 2008 All ri
7、ghts reserved iii 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 sub
8、ject 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 (I
9、EC) 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 commit
10、tees 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
11、 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 ap
12、proval 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 ISO 26431-1:2008(E) iv ISO 2008 All rights reservedIntroduction This International Standard comprises SMP
13、TE 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 revie
14、w national standards and recommendations. ISO 26431-1:2008(E) ISO 2008 All rights reserved 11 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 digita
15、l 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, th
16、rough 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 editio
17、n 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 ins
18、tallation. 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
19、 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 Me
20、asurements 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 t
21、he 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. Page 1 of 5 pages SMPTE 431-1-2006 Copyright 2006 by THE SOCIETY OF MOTI
22、ON PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved April 18, 2006 SMPTE STANDARD for D-Cinema Quality Screen Luminance Level, Chromaticity and Uniformity ISO 26431-1:2008(E) 2 ISO 2008 All rights reservedSMPTE 431-1-2006 Page 2 of 5 pages 4.2 Measurem
23、ent 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
24、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)
25、 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 sha
26、ll be 2 or less. The photometer shall have an accuracy of 0.5 cd/m ( 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 t
27、ype Screen chromaticity shall be measured with a spot spectroradiometer with an acceptance angle of 2 or less. It shall report values in CIE x, y coordinates, with an accuracy of 0.002 or better for both x and y. NOTE As there are meters available that measure both luminous flux and chromaticity, th
28、is may physically be the same meter defined in section 4.4. 5 Specifications Measurements taken from each location specified in section 4.3 shall be within the limits given in this section. 5.1 Luminance, absolute The absolute luminance is that value measured at the screen center as taken with a met
29、er meeting the criteria of section 4.4. The nominal value for screen luminance is 48.0 cd/m (14.0 fL). The allowable variation for each performance class is given in table 1. 5.2 Luminance, uniformity The screen luminance shall be symmetrically distributed about the geometric center of the screen, a
30、nd shall exhibit no abrupt changes. The luminance value at the sides and corners defined in section 4.2 is expressed as a percentage of the value at the screen center. The meter used shall meet the criteria of section 4.4. The allowable variation for each performance class is given in table 1. 5.3 W
31、hite point chromaticity The white point chromaticity is that value measured in the center of the screen as taken with a meter meeting the criteria of section 4.5. The white light reflected from the screen shall have a nominal chromaticity value of x = .314, y = .351. The allowable variation for each
32、 performance class is given in table 1. ISO 26431-1:2008(E) ISO 2008 All rights reserved 3 SMPTE 431-1-2006 Page 3 of 5 pages Table 1 Performance levels by class Section Parameter Reference Review room Theater 5.1 Luminance, center 100% white 48.0 cd/m (14.0 fL) 3.5 cd/m ( 1.00 fL) 10.2 cd/m ( 3.00
33、fL) 5.2 Luminance sides 85% of center 80% to 90% of center 75% to 90% of center 5.2 Luminance corners 85% of center 80% to 90% of center not specified 5.3 White chromaticity, center x = .314 y = .351 .002 x . 002 y .006 x .006 y ISO 26431-1:2008(E) 4 ISO 2008 All rights reservedSMPTE 431-1-2006 Page
34、 4 of 5 pages Annex A (informative) Additional data A.1 “Normal” release Standardized values for luminance and chromaticity are required in order to make images match the appearance intended by the creators of the content, and to facilitate interchangeability of the same content from one theatre to
35、another as well as from one showing to the next within the same theatre. It is not possible to specify a “normal” digital release in terms of its optical density and other objective measurements due to its intangible nature and because of the difficulties of specifying artistic quality in scientific
36、 terms. Accordingly, the normal release is defined as that which conveys the desired artistic impression when projected as described by this standard. A.2 Acceptable luminance range The range of acceptable luminance levels is limited by a minimum value, below which the visual process becomes less ef
37、ficient such that the dynamic range of scenes appears compressed, and by a maximum value, above which the black level becomes unnaturally elevated. The permissible luminance range is limited by the criterion that a digital release must provide acceptable quality when projected at any luminance withi
38、n the specified range. Users are reminded that screen luminance decreases as a function of bulb age, dirt on optics, dirt on the screen, etc. A.3 Matching luminance of different formats It may be necessary to adjust projector light output to compensate for the different image sizes and magnification
39、 used when projecting different picture formats. The projector light source should be capable of achieving the specified screen luminance for the format with the least light efficiency. When projecting more light-efficient formats, adjustment may be made by reducing lamp current or by use of attenua
40、tors in the light beam to reduce the screen luminance to within the standardized range. A.4 Luminance distribution on gain screens The screen luminance should be symmetrically distributed about the geometric center of the screen. The luminance of any point on the screen between the center and the ed
41、ges, as measured from any seat in the middle row, should not exceed the screen center reading. For screens with a gain factor of 1.1 or more, the screen should be curved for light uniformity as described in SMPTE RP 95. A more complete measurement of screen luminance distribution is described in SMP
42、TE RP 98 and is recommended for new or revised installations. A.5 White chromaticity uniformity The white chromaticity should be symmetrically distributed about the geometric center of the screen, and should exhibit no abrupt changes. The value is measured at the four corners defined in section 4.2,
43、 and is computed separately for each location, as the x or y value for that location, minus the x or y value at the screen center. The identical meter used to measure white point chromaticity (section 5.3) should also be used to measure white chromaticity uniformity. While the goal of a good D-cinem
44、a presentation is review room quality, the allowable variation for each performance class is shown below: Parameter Reference Review room Theater White chromaticity corners within .000 x .000 y of center within . 008 x . 008 y of center within .015 x .015 y of center A.6 Incident vs. reflected light
45、 This standard is based upon measurement of an installed projection system, consisting of a projector, a room, and a screen, not merely a projector. Screen aging or yellowing may not be uniform across the screen surface and may result in luminance or chromaticity variation greater than expected. Lik
46、ewise, misadjustment of the projector light source, optical system, or use of a non-optimum screen configuration may cause luminance readings taken at various locations in the ISO 26431-1:2008(E) ISO 2008 All rights reserved 5 SMPTE 431-1-2006 Page 5 of 5 pages seating area and on various areas of t
47、he screen to exceed the screen center reading taken as described in section 5.1 (hot spots). In cases where excessive differences are measured across the image area, it may be helpful to identify the source of the problem by directly measuring the incident light from the projector. However this is u
48、nderstood to be a diagnostic aid only; readings taken this way are not in keeping with this standard. Generally speaking, in order for an installation in an auditorium to meet a specific performance level, the projector itself will likely have to meet a tighter performance specification to allow for
49、 the contributions of the port glass and screen (or provide the ability to compensate for these effects). A.7 Stray light and contrast Stray light from foot lights, exit signs, and the like causes a decrease in contrast and impairs the desired artistic impression. As a guideline, no illuminated area with a luminance greater than 3.4 cd/m2 (1.0 fL) should be directly visible from the audience. Stray light reflected on to the screen from other surfaces or seats in the room will also redu
