1、BSI Standards PublicationBS ISO 7832:2014Cinematography Photoelectric output factor ofphotographic-type audio-leveltest films Measurement andcalibrationBS ISO 7832:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 7832:2014.The UK participation in its prepar
2、ation was entrusted to TechnicalCommittee CPW/36, Cinematography.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication.
3、The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 83230 7ICS 37.060.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31
4、 October 2014.Amendments issued since publicationDate Text affectedBS ISO 7832:2014 ISO 2014Cinematography Photoelectric output factor of photographic-type audio-level test films Measurement and calibrationCinmatographie Facteur de sortie photolectrique des films dessai de niveau sonore de type opti
5、que Mesurage et talonnageINTERNATIONAL STANDARDISO7832Second edition2014-10-01Reference numberISO 7832:2014(E)BS ISO 7832:2014ISO 7832:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specified, no part of this publication may be reprod
6、uced 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 body in the country of the requester.
7、ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 7832:2014ISO 7832:2014(E) ISO 2014 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative references 13 Terms, definitio
8、ns, and symbols 14 Method of measurement 25 Method of calibration 25.1 DC method 25.2 AC method . 26 Calibration procedure . 27 Calibrating reproducer 2Annex A (normative) DC and AC calibration . 6BS ISO 7832:2014ISO 7832:2014(E)ForewordISO (the International Organization for Standardization) is a w
9、orldwide 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
10、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.The procedures used to develop this
11、 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 Dir
12、ectives, 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 deve
13、lopment 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 an endorsement.For an explanation on the meaning of ISO
14、 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 informationThe committee responsible for this document is ISO/TC 36, Cinematogr
15、aphy.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 STANDARD ISO 7832:2014(E)Cinematography Photoelectric output factor of photographic-type audio-level test films Measu
16、rement and calibration1 ScopeThis 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 calibrating sound reproducer. It is applicable to both variable area- an
17、d 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 sound reproducers and the photoelectric output factor of different so
18、und 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 referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its a
19、pplication. 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-picture release prints Position and dimensionsISO 4243, Cinematograph
20、y Picture image area and photographic sound record on 16 mm motion-picture release prints Positions and dimensionsISO 6025, Cinematography Analogue photographic sound test films, 35 mm and 16 mm Specifications3 Terms, definitions, and symbolsFor the purposes of this document, the following terms and
21、 definitions apply.3.1voltage outputsV1, V2, V3, V4output 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 is essentially linear3.2maximum photoelectric outputMPOvoltage difference obtained
22、between full illumination of the photoelectric receptor by the scanning beam and complete occulting of the scanning beam, as defined by V1and V4in Figures 1 and 23.3peak-to-peak voltagePVvoltage difference observed for a sound level test film between the maximum output at the crest of a sine wave (+
23、 peak) and the minimum output at the trough of a sine wave (peak), as defined by V2and V3in Figures 1 and 2 ISO 2014 All rights reserved 1BS ISO 7832:2014ISO 7832:2014(E)3.4photoelectric output factorPOFratio of the PV from the film, as defined in 3.3, to the maximum output of the reproducer when re
24、producing an audio level test film on a calibrating reproducer, as defined in 3.2Note 1 to entry: An ideal test film would have a photoelectric output factor of 1,0 which is a theoretical value that cannot be obtained in photographic sound recording due to sound track image density, base density, an
25、d fog density.4 Method of measurement4.1 The photoelectric output factor shall be measured on a calibrating reproducer, as described in Clause 7, with the required instrumentation arranged in accordance with Annex A and Figures 3 and 4.4.2 The signal frequencies of the test film shall be as specifie
26、d in ISO 6025.5 Method of calibrationTwo alternative methods of calibration are given.5.1 DC methodCalibration is carried out by comparing the steady-state values of full scanning beam illumination on the phototransducer with complete occultation (see Figure 1 and A.2).5.2 AC methodCalibration is ca
27、rried 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 audio-level test film (see Figure 2 and A.3).6 Calibration procedureCalibration requires electrical measurements,
28、 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 as a percentage of the maximum output of the reproducer.6.1 With the calibrating reproducer conforming to ISO 2
29、939 or ISO 4243 and with no film in the reproducer, measure the voltage difference between V1and V4, as defined in 3.2.6.2 With the audio-level test film running through the calibrating reproducer, measure the peak-to-peak voltage difference between V2and V3, as defined in 3.3.6.3 Calculate the phot
30、oelectric output factor (POF) of the audio-level test film using Formula (1):POFPVMPO= (1)7 Calibrating reproducer7.1 The calibrating reproducer shall comply with the flutter specification of ISO 6025 for the audio-level test film being calibrated.2 ISO 2014 All rights reservedBS ISO 7832:2014ISO 78
31、32:2014(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 plane shall be within 1 % of the nominal value specified in ISO 2939 or ISO 4243.7.4 Uniformity of illumination across the
32、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 of calculated corrections to avoid errors is not permitted.12Key1 full illumination (without film)2 no illuminationFigur
33、e 1 Calibration waveforms DC methodFigure 2 Calibration waveforms AC method ISO 2014 All rights reserved 3BS ISO 7832:2014ISO 7832:2014(E)NOTE This shutter wheel is designed to give equal on-and-off durations and may be conveniently driven by any small DC motor. The shutter, containing 24 elements a
34、s 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)47812356891011Key1 exciter lamp 7 cell2 slit 8 operational amplifier (DC)3 lens 9 oscilloscope with DC response4 motor 10 peak readin
35、g AC voltmeter5 shutter wheel (AC method only) 11 electronic DC voltmeter (DC method only)6 film plane Figure 4 Equipment required to establish photoelectric output factor ISO 2014 All rights reserved 5BS ISO 7832:2014ISO 7832:2014(E)Annex A (normative) DC and AC calibrationA.1 InstructionWhen using
36、 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 relevant measuring frequency, as specified in ISO 6025, and that the combination have a linear voltage versus illumination relationship. If a silicon cell i
37、s 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, 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
38、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 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 res
39、ponse, 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 calibrationA.2.1 The photoreproducer shall, for constant illumination, have equal electrical peak output at the measuring frequency, as specified in ISO 6025
40、 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 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
41、 the output voltage for direct illumination of the phototransducer by the scanning beam with the output voltage obtained by complete occulting 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 out
42、put 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 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 calibrationA.3.1 Provision shall
43、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 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 int
44、erruption of the scanning beam matches the frequency of the sound record on the audio-level test film ( 5 %).6 ISO 2014 All rights reservedBS 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 u
45、sing a peak reading AC voltmeter. This amplitude reading shall be defined as the MPO of the reproducer.A.3.4 With the audio-level test 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
46、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.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
47、from the following factors:a) Transmission factor (T) is a numerical difference obtained between the lightest (Thi) and darkest (Tlo) sections of the sine wave on the sound record print, using a correctly adjusted densitometer (Thi Tlo).b) Reduction factor (R) is the ratio between 100 % modulation o
48、f a variable-area sound record and the width of the reproducer slit, as defined by the appropriate International Standard 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
49、) 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 applicable to both calibration methodsA.4.1 MeasurementsIt is advisable to take at least two or three separate measurements and compute the mean value.A.4.2 Scanning beamThe tolerance affecting the accu
