ISO 7832:2014

Cinematography - Photoelectric output factor of photographic-type audio-level test films - Measurement and calibration

ISO 7832:2014 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- and variable density-type sound records with a silver audio track. It also specifies the performance of a calibrating audio reproducer.

Cinématographie — Facteur de sortie photoélectrique des films d'essai de niveau sonore de type optique — Mesurage et étalonnage

General Information

• Status: Published
• Publication Date: 30-Sep-2014
• ICS: 37.060.20 - Motion picture films. Cartridges
• Technical Committee: ISO/TC 36 - Cinematography
• Drafting Committee: ISO/TC 36/WG 3 - Audio technology
• Current Stage: 9060 - Close of review
• Completion Date: 02-Sep-2030

Relations

• Revises: ISO 7832:1987 - Cinematography - Photoelectric output factor of photographic-type audio-level test films - Measurement and calibration
• Effective Date: 18-May-2013

Overview

ISO 7832:2014 specifies methods for measuring and calibrating the photoelectric output factor (POF) of single‑channel analogue photographic‑type audio‑level test films in all gauges. Applicable to both variable area and variable density silver audio tracks, the standard defines measurement procedures using a calibrating sound reproducer and specifies the required performance, alignment and instrumentation for accurate calibration.

Key topics and requirements

• Scope: Calibration and measurement of POF for photographic‑type audio‑level test films (single channel; silver audio tracks).
• POF definition: POF = PV / MPO, where PV is the film’s peak‑to‑peak output and MPO is the reproducer’s maximum photoelectric output. (An ideal POF = 1.0 is theoretical.)
• Two calibration methods:
  • DC method: Compare steady‑state full illumination vs complete occulting of the scanning beam using a DC voltmeter and ensure linear voltage vs illumination behaviour (Annex A).
  • AC method: Use a mechanical shutter wheel to interrupt the scanning beam at the test film frequency; measure peak‑to‑peak amplitude with a true‑peak AC voltmeter.
• Instrumentation: True‑peak reading AC voltmeter, DC voltmeter, oscilloscope with DC response, phototransducer (e.g., silicon cell with zero‑input‑impedance amplifier), shutter wheel (for AC), and provision for warm‑up and drift checks.
• Calibrating reproducer performance:
  • Must meet flutter specification of ISO 6025 for the film gauge.
  • Scanning beam width at film plane within ±1% of values in ISO 2939 or ISO 4243.
  • Illumination uniformity and phototransducer point‑to‑point efficiency constant within ±5% (use of calculated corrections is not permitted).
• Measurement practice: Take multiple readings, check drift, use true‑peak meters (average meters with pseudo‑peak correction are not acceptable). Harmonic distortion up to 3% is tolerated.

Applications and users

ISO 7832:2014 is used to:

• Calibrate audio‑level test films for laboratory and field verification of motion‑picture sound reproducers.
• Establish reference levels on standard program‑level meters in projection and post‑production environments.
• Support quality assurance in film laboratories, cinema service/maintenance, archival preservation, and equipment manufacturing. Primary users include projection engineers, film laboratory technicians, calibration laboratories, archivists, standards bodies and audiovisual equipment designers.

Related standards

• ISO 6025 - Analogue photographic sound test films (35 mm and 16 mm) - specifications
• ISO 2939 - Picture image area on 35 mm release prints - position and dimensions
• ISO 4243 - Picture area and photographic sound record on 16 mm release prints - positions and dimensions

Keywords: ISO 7832:2014, photoelectric output factor, audio‑level test films, calibration, calibrating reproducer, variable area, variable density, photographic sound, DC method, AC method.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7832
Second edition
2014-10-01
Cinematography — Photoelectric
output factor of photographic-type
audio-level test films — Measurement
and calibration
Cinématographie — Facteur de sortie photoélectrique des films
d’essai de niveau sonore de type optique — Mesurage et étalonnage
Reference number
©
ISO 2014
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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Published in Switzerland
ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 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 . 6
Foreword
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committee has been established has the right to be represented on that committee. International
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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
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee 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 reserved

INTERNATIONAL STANDARD ISO 7832:2014(E)
Cinematography — Photoelectric output 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 calibrating
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 sound
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 normatively 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-picture 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, and symbols
For the purposes of this document, the following terms and definitions apply.
3.1
voltage outputs
V, V, V, V
1 2 3 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 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 and V in Figures 1 and 2
1 4
3.3
peak-to-peak voltage
PV
voltage difference observed 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 and V in
2 3
Figures 1 and 2
3.4
photoelectric output factor
POF
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 cannot 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 accordance with Annex A and Figures 3 and 4.
4.2 The signal frequencies of the test film shall be as specified in ISO
...