1、BSI Standards Publication BS ISO 7832:2014 Cinematography Photoelectric output factor of photographic-type audio-level test films Measurement and calibrationBS ISO 7832:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 7832:2014. The UK participation in it
2、s preparation was entrusted to Technical Committee CPW/36, Cinematography. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct
3、 application. The British Standards Institution 2014. Published by BSI Standards Limited 2014 ISBN 978 0 580 83230 7 ICS 37.060.20 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Str
4、ategy Committee on 31 October 2014. Amendments issued since publication Date Text affectedBS ISO 7832:2014 ISO 2014 Cinematography Photoelectric output factor of photographic-type audio-level test films Measurement and calibration Cinmatographie Facteur de sortie photolectrique des films dessai de n
5、iveau sonore de type optique Mesurage et talonnage INTERNATIONAL STANDARD ISO 7832 Second edition 2014-10-01 Reference number ISO 7832:2014(E)BS ISO 7832:2014ISO 7832:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 All rights reserved. Unless otherwise specified, no part
6、 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 ISOs member bod
7、y 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 SwitzerlandBS ISO 7832:2014ISO 7832:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv 1 Scope .
8、 1 2 Normative references 1 3 Terms, definitions, and symbols 1 4 Method of measurement 2 5 Method of calibration 2 5.1 DC method 2 5.2 AC method . 2 6 Calibration procedure . 2 7 Calibrating reproducer 2 Annex A (normative) DC and AC calibration . 6BS ISO 7832:2014ISO 7832:2014(E) Foreword ISO (the
9、 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 committe
10、e 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 electrotechni
11、cal 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 i
12、n 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.
13、 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
14、 an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The commit
15、tee responsible for this document is ISO/TC 36, Cinematography. This second edition cancels and replaces the first edition (ISO 7832:1987), of which it constitutes a minor revision.iv ISO 2014 All rights reservedBS ISO 7832:2014INTERNATIONAL ST ANDARD ISO 7832:2014(E) Cinematography Photoelectric ou
16、tput factor of photographic-type audio-level test films Measurement and calibration 1 Scope This International Standard specifies a method of measuring and calibrating the photoelectric output factor of single channel analogue photographic-type audio-level test films in all gauges, using a calibrati
17、ng sound reproducer. It is applicable to both variable area- and variable density-type sound records with a silver audio track. It also specifies the performance of a calibrating audio reproducer. Calibrated audio-level test films are employed to measure the precise output level of photographic soun
18、d reproducers and the photoelectric output factor of different sound records. They are also employed to establish a reference level on a standard program level meter, should that be appropriate for the installation in use. 2 Normative references The following documents, in whole or in part, are norm
19、atively 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 2939, Cinematography Picture image area on 35 mm motion-p
20、icture release prints Position and dimensions ISO 4243, Cinematography Picture image area and photographic sound record on 16 mm motion-picture release prints Positions and dimensions ISO 6025, Cinematography Analogue photographic sound test films, 35 mm and 16 mm Specifications 3 Terms, definitions
21、, and symbols For the purposes of this document, the following terms and definitions apply. 3.1 voltage outputs V 1 , V 2 , V 3 , V 4 output voltage levels from the calibrating sound reproducer, measured at a point in the circuitry where the voltage relationship to the amplitude of the sound record
22、is essentially linear 3.2 maximum photoelectric output MPO voltage difference obtained between full illumination of the photoelectric receptor by the scanning beam and complete occulting of the scanning beam, as defined by V 1and V 4in Figures 1 and 2 3.3 peak-to-peak voltage PV voltage difference o
23、bserved for a sound level test film between the maximum output at the crest of a sine wave (+ peak) and the minimum output at the trough of a sine wave (peak), as defined by V 2and V 3in Figures 1 and 2 ISO 2014 All rights reserved 1BS ISO 7832:2014ISO 7832:2014(E) 3.4 photoelectric output factor PO
24、F ratio of the PV from the film, as defined in 3.3, to the maximum output of the reproducer when reproducing an audio level test film on a calibrating reproducer, as defined in 3.2 Note 1 to entry: An ideal test film would have a photoelectric output factor of 1,0 which is a theoretical value that c
25、annot be obtained in photographic sound recording due to sound track image density, base density, and fog density. 4 Method of measurement 4.1 The photoelectric output factor shall be measured on a calibrating reproducer, as described in Clause 7, with the required instrumentation arranged in accord
26、ance with Annex A and Figures 3 and 4. 4.2 The signal frequencies of the test film shall be as specified in ISO 6025. 5 Method of calibration Two alternative methods of calibration are given. 5.1 DC method Calibration is carried out by comparing the steady-state values of full scanning beam illumina
27、tion on the phototransducer with complete occultation (see Figure 1 and A.2). 5.2 AC method Calibration is carried out by means of an occulting shutter interrupting the scanning beam illumination on the photoelectric transducer, the shutter operating at the same nominal frequency as that of the audi
28、o-level test film (see Figure 2 and A.3). 6 Calibration procedure Calibration requires electrical measurements, which show the peak-to-peak voltage output obtained, using a true-peak reading voltmeter, when running an audio-level test film through a calibrating reproducer. This voltage is expressed
29、as a percentage of the maximum output of the reproducer. 6.1 With the calibrating reproducer conforming to ISO 2939 or ISO 4243 and with no film in the reproducer, measure the voltage difference between V 1and V 4 , as defined in 3.2. 6.2 With the audio-level test film running through the calibratin
30、g reproducer, measure the peak-to- peak voltage difference between V 2and V 3 , as defined in 3.3. 6.3 Calculate the photoelectric output factor (POF) of the audio-level test film using Formula (1): = (1) 7 Calibrating reproducer 7.1 The calibrating reproducer shall comply with the flutter specifica
31、tion of ISO 6025 for the audio- level test film being calibrated.2 ISO 2014 All rights reservedBS ISO 7832:2014ISO 7832:2014(E) 7.2 The location, azimuth, and focus of the scanning beam shall be aligned using the appropriate photographic test film. 7.3 The width of the scanning beam at the film plan
32、e shall be within 1 % of the nominal value specified in ISO 2939 or ISO 4243. 7.4 Uniformity of illumination across the width of the scanning beam, together with the point-to-point photon efficiency of the phototransducer, shall be constant within 5 % when using a snake track test film. NOTE The use
33、 of calculated corrections to avoid errors is not permitted. 1 2 Key 1 full illumination (without film) 2 no illumination Figure 1 Calibration waveforms DC method Figure 2 Calibration waveforms AC method ISO 2014 All rights reserved 3BS ISO 7832:2014ISO 7832:2014(E) NOTE This shutter wheel is design
34、ed to give equal on-and-off durations and may be conveniently driven by any small DC motor. The shutter, containing 24 elements as shown, generates a 400 Hz tone at 1 000 r/min and a 1 000 Hz tone at 2 500 r/min. Figure 3 Shutter wheel4 ISO 2014 All rights reservedBS ISO 7832:2014ISO 7832:2014(E) 4
35、7 8 1 2 3 5 6 8 9 10 11 Key 1 exciter lamp 7 cell 2 slit 8 operational amplifier (DC) 3 lens 9 oscilloscope with DC response 4 motor 10 peak reading AC voltmeter 5 shutter wheel (AC method only) 11 electronic DC voltmeter (DC method only) 6 film plane Figure 4 Equipment required to establish photoel
36、ectric output factor ISO 2014 All rights reserved 5BS ISO 7832:2014ISO 7832:2014(E) Annex A (normative) DC and AC calibration A.1 Instruction When using the DC method of calibration, it is essential that the combination of phototransducer and amplifier give the same output at 0 Hz or DC and the rele
37、vant measuring frequency, as specified in ISO 6025, and that the combination have a linear voltage versus illumination relationship. If a silicon cell is used as the phototransducer, it shall be connected to a zero input impedance operational amplifier. A.1.1 When using the AC method of calibration,
38、 a specially designed shutter wheel finished in non- reflecting black (see Figure 3) shall be inserted in the path of the scanning beam. The width of the shutter blades shall be the same as the distance between them and their dimensions shall be considerably larger than those of the scanning beam at
39、 the point of interruption. A.1.2 The measuring instruments required include a DC voltmeter, a peak reading AC voltmeter, and an oscilloscope with a DC response, connected as shown in Figure 4. It is essential to allow the system sufficient time to warm up before any measurements are taken. A.2 DC c
40、alibration A.2.1 The photoreproducer shall, for constant illumination, have equal electrical peak output at the measuring frequency, as specified in ISO 6025 and at 0 Hz. A.2.2 The combination of the phototransducer and its operational amplifier shall be evaluated for drift and shown to have nominal
41、 effect ( 5 %) over the time interval required for measuring. A.2.3 With no film in the reproducer, measure the maximum photoelectric output (MPO) by comparing the output voltage for direct illumination of the phototransducer by the scanning beam with the output voltage obtained by complete occultin
42、g of the scanning beam, using a DC voltmeter. A.2.4 With the audio-level test film running through the reproducer, measure the peak-to-peak amplitude of the output signal voltage using a peak reading AC voltmeter. A.2.5 Repeat the measurement described in A.2.3 to verify that the drift is within the
43、 tolerance specified in A.2.2. A.2.6 Calculate the photoelectric output factor (POF) using the procedure described in 6.3. A.3 AC calibration A.3.1 Provision shall be made on the calibrating reproducer for the scanning beam to be interrupted by a mechanical shutter (see Figure 3 and A.1.2), designed
44、 so as to give equal on-and-off durations at a nominally constant frequency. A.3.2 The shutter shall have provision for speed adjustment so that the frequency of interruption of the scanning beam matches the frequency of the sound record on the audio-level test film ( 5 %).6 ISO 2014 All rights rese
45、rvedBS ISO 7832:2014ISO 7832:2014(E) A.3.3 With no film in the reproducer and the shutter operating, measure the peak-to-peak amplitude of the output signal voltage using a peak reading AC voltmeter. This amplitude reading shall be defined as the MPO of the reproducer. A.3.4 With the audio-level tes
46、t film running through the reproducer and the shutter removed or locked open, measure the peak-to-peak amplitude of the output signal voltage on the same peak reading AC voltmeter. A.3.5 Repeat the measurement described in A.3.3 to verify that the drift is within the tolerance specified in A.2.2. A.
47、3.6 Calculate the POF using the procedure described in 6.3. NOTE If a theoretically derived POF is required, the result can be calculated for variable-area sound records from the following factors: a) Transmission factor (T) is a numerical difference obtained between the lightest (T hi ) and darkest
48、 (T lo ) sections of the sine wave on the sound record print, using a correctly adjusted densitometer (T hi T lo ). b) Reduction factor (R) is the ratio between 100 % modulation of a variable-area sound record and the width of the reproducer slit, as defined by the appropriate International Standard
49、 for the gauge. This reduction factor does not apply to variable-density sound records since the track width is greater than the width of the reproducer slit. c) Film modulation (M) is, for variable-area sound records, the modulation of the test film measured geometrically in relation to 100 % modulation as defined in the appropriate International Standards referenced in Clause 2. d) The theoretical POF is determined by Formula (A.1): POF (theoretical) = T R M (A.1) A.4 Precautions appl
