ISO 2721 pdf download Photography — Film-based cameras — Automatic controls of exposure
automatic setting of camera exposureaction ofthe automatic exposure controlintended to maintain substantially constant exposure at the focalplane for a preset film speed for all values offield luminance within the exposure capabilities ofthe camera
Note 1 to entry: The film speed setting may be made manually or may be automatically sensed from the film orits container.
Note 2 to entry: Operation of the control may require the operator’s participation in adjusting an indicator to afiducial point or condition for set-point recognition, but should not require him to read light value indications andtransfer the information to another mechanism having similar fiducial markings.
exposure capability of cameradifference between the maximum exposure value for which the camera can provide nominal focalplane exposure and the minimum exposure value for which the camera can provide nominal focal-planeexposure, both for the film speed ISO 100/21
Note 1 to entry: When describing the exposure capability of a camera, the film speed should be indicated
Ifthe camera has scales for f-number, exposure time, exposure value, or film speed, the numerical valuesaccording to ISO 2720 shall be applied.
4.2 0ut-of-range indication
For cameras designed to use colour reversal films, automatic indication,for example by an optical signain the viewfinder, should be displayed when the field luminance exceeds the exposure capability ofthe camera by more than 1 Ey (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 subiectuminance below 4 cd/m2 and above 4096 cd/m2, 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 toresult in an exposure longer than approximately 1/30 s. This signal need not be provided if the cameracannot give an exposure longer than 1/30 s without the photographer being aware of it.
4.3 The sensors of exposure controls
The spectral sensitivity of the system response in the camera shall manifest no discontinuities withinthe visible spectrum (380 nm to 780 nm).
4.3.2Spectral sensitivity tests
For cameras designed to be used in daylight, tungsten light, and with other artificial sources, the ratioof the responses of the light sensors including optical systems to field luminances of distributiontemperature 2856 K compared with those at 4700 K shall be 1,0* 0 26 (corresponding to + 1/3 Ev). Notmore than 10 % of the total response of the light sensors, including optical systems, should be due towavelengths longer than 700 nm when the sensors are exposed to a light source of equal energy at allwavelengths. Not more than 10 % of the total response of the sensors should be due to wavelengthsshorter than 380 nm when tested in the same manner.