ISO 2721:2013 pdf download.Photography – – Film-based cameras -Automatic controls of exposure.
ISO 2721 specifies the exposure at the focal plane of film-based cameras for values of two exposure parameters, i.e. field luminance and film speed, and also describes methods of evaluating other photometric characteristics, such as the acceptance angles of the photoelectric system.
This International Standard applies to automatic exposure control systems which are built into film- based cameras or coupled with them to regulate the exposure in the focal plane as a function of the several exposure parameters. The mechanism can control either the focal-plane illuminance or the exposure-time interval or both. Pointer (or needle) matching systems are included in this International Standard even though they are not fully automatic. This standard is not applicable to digital cameras.
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.
IEC 60068-2-6, Environmental testing — Part 2-6: Tests — Test Fc: Vibration (sinusoidal) IEC 60068-2-2 7, Environmental testing — Part 2-27: Tests — Test Eu and guidance: Shock
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
exposure in the focal plane
3.2
automatic setting of camera exposure
action of the automatic exposure control intended to maintain substantially constant exposure at the focal plane for a preset film speed for all values of field luminance within the exposure capabilities of the camera
Note 1 to entry: The film speed setting may be made manually or may be automatically sensed from the film Or its container.
Note 2 to entry: Operation of the control may require the operator’s participation in adjusting an indicator to a fiducial point or condition for set-point recognition, but should not require him to read light value indications and transfer the information to another mechanism having similar fiducial markings.
3.3
exposure capability of camera
difference between the maximum exposure value for which the camera can provide nominal focal- plane exposure and the minimum exposure value for which the camera can provide nominal focal-plane exposure, both for the film speed ISO 100/21°
Note Ito entry: When describing the exposure capability of a camera, the film speed should be indicated.
4 Specific requirements
4.1 Scales
If the camera has scales for f-number, exposure time, exposure value, or film speed, the numerical values according to 150 2720 shall be applied.
4.2 Out-of-range indication
For cameras designed to use colour reversal films, automatic indication, for example by an optical signal in the viewfinder, should be displayed when the field luminance exceeds the exposure capability of the camera by more than 1 Ev (1 exposure value = 1 step) in either over-exposure or under-exposure. This indication need only be provided if the exposure capability of the camera does not cover subject luminance below 4096 cd/m2 and above 4096 cd/rn2. Tests are made with a uniform source.
In addition, a long exposure signal should be provided to indicate when the field luminance is such as to result in an exposure longer than approximately 1/30 s. This signal need not be provided if the camera cannot give an exposure longer than 1/30 s without the photographer being aware of it.
4.3 The sensors of exposure controls
4.3.1 Spectral sensitivity
The spectral sensitivity of the system response in the camera shall manifest no discontinuities within the visible spectrum (380 nm to 780 nm).
4.3.2 Spectral sensitivity tests.ISO 2721 pdf download.