ISO 2720:1974 PDF

Name: ISO 2720:1974 — Photography — General purpose photographic exposure meters (photoelectric type) — Guide to product specification
SKU: ISO 2720:1974
Price: 25 EUR
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Photography — General purpose photographic exposure meters (photoelectric type) — Guide to product specification

Название (английский):

ISO 2720:1974

Photography — General purpose photographic exposure meters (photoelectric type) — Guide to product specification

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 10
Дата публикации:: 1 августа 1974 г.
Издание:: ISO IS 2720 edition 1 version 1
ICS:: 37.040.10

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Описание (английский):

Specified are calibration levels and test conditions for general-purpose photoelectric exposure meters which measure reflected or incident light, or both, in determining photographic exposure for camera use. The specifications apply to exposure meters containing a light-sensitive element, and indicating electrical instrument, a directional system and a calculator to correlate the meter indications with the camera exposure settings.

Abstract

Похожие стандарты

Другие стандарты ISO

Overview

ISO 2720:1974 - "Photography - General purpose photographic exposure meters (photoelectric type) - Guide to product specification" defines calibration levels and test conditions for photoelectric exposure meters used to determine camera exposure. It applies to meters that measure reflected light, incident light, or both, and that contain a light‑sensitive element, an indicating electrical instrument, a directional system and a calculator to correlate meter readings with camera settings. The standard does not cover automatic or semi‑automatic camera exposure control.

Key topics and technical requirements

Scope and markings

Requirement for clear nomenclature, film speed (logarithmic/arithmetic, ISO designations), exposure value (EV/STEP) and aperture/shutter scales compatible with clause 6 formulae.

Calibration and constants

Defines calibration constants (K for reflected meters, C for incident meters) and permissible marking/labeling of these values.

Light sources and colour temperature

Reference lamp/filter combinations to simulate practical daylight/tungsten mix (examples: correlated colour temperature near 4 700 K; tungsten lamp at 2 855.6 K with filter yielding transmittance 0.259).

Spectral sensitivity

Continuous spectral response required over 400–700 nm; spectral response assessed against a colour‑conversion filter and CIE standard photometric observer.

Performance tests

Response time at normal and low light levels; fatigue of photo‑electric element; low‑light recovery.
Shock resistance: one half‑sine impact at 75 g, duration 3.5 ms, applied to six faces.
Vibration: IEC 68‑2‑6 style vibration (30→100→30 Hz cycles, applied in three orthogonal axes).
Humidity: prolonged dark exposure at high humidity (e.g., 40 h at 35 °C, 90% RH) and subsequent calibration check.
Temperature: checks at 0 °C to +40 °C and extremes (−35 °C and +50 °C) for indication drift.

Directional characteristics

Defines specific/oblique acceptance angles and average acceptance for meter directional response.

Practical considerations

Battery life guidance, zero adjustment, bearing friction elimination during readings.

Applications and users

Manufacturers of photoelectric exposure meters and handheld light meters

Test laboratories and calibration facilities verifying meter accuracy, spectral response and environmental resilience

Camera and photographic equipment designers ensuring compatibility of meter output with film speed and exposure calculators

Photographers and rental houses that require certified metering equipment for critical exposure work

Related standards and references

ISO/TC 42 (Photography) - technical committee responsible for development

IEC Publication 68‑2‑6 (Vibration) and IEC 68‑2‑27 (Shock) - referenced test procedures

CIE standard photometric observer (for spectral assessments)

Keywords: ISO 2720:1974, photographic exposure meters, photoelectric exposure meters, calibration, test conditions, reflected light meter, incident light meter, spectral sensitivity, exposure value, film speed.

ISO 2720:1974 PDF

Abstract

Похожие стандарты

Overview

Key topics and technical requirements

Applications and users

Related standards and references

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