A number of factors need to be considered when buying and implementing a CCTV system. Which of the following is the primary factor in determining whether a lens should have a manual iris or an auto-iris?

A.
If the camera must be able to move in response to commands

B.
If the environment has fixed lighting

C.
If objects to be viewed are wide angle, such as a parking lot, or narrow, such as a door

D.
The amount of light present in the environment

Explanation:
B: CCTV lenses have irises, which control the amount of light that enters the lens. If the environment has fixed lighting, then a lens with a manual iris can be
used. Manual iris lenses cannot self-adjust to changes in light. They have to be manually turned and controlled by moving a ring around the lens. If the
environment has changing light, as in an outdoor setting, then an auto-iris lens should be used. As the environment brightens, this is sensed by the iris, which
automatically adjusts itself. Security personnel will configure the CCTV to have a specific fixed exposure value, which the iris is responsible for maintaining. On a
sunny day, the iris lens closes to reduce the amount of light entering the camera, while at night, the iris opens to capture more lightjust like our eyes.
A is incorrect because a camera’s ability to move in response to security personnel commands determines its mounting requirements. Cameras can be
implemented in a fixed mounting or a mounting that allows the cameras to move when necessary. A fixed camera cannot move in response to security personnel
commands, whereas cameras that provide PTZ capabilities can pan, tilt, or zoom as necessary.
C is incorrect because the angle of items to be viewed influences the focal length required of the lens. The focal length of a lens defines its effectiveness in
viewing objects from a horizontal and vertical view. The focal length value relates to the angle of view that can be achieved. Short focal length lenses provide
wider-angle views, while long focal length lenses provide a narrower view. The size of the images shown on a monitor, along with the area covered by one
camera, is defined by the focal length. For example, if a company implements a CCTV camera in a warehouse, the focal length lens should be between 2.8 and
4.3 millimeters (mm) so that the whole area can be captured. If the company implements another CCTV camera that monitors an entrance, then the lens value
should be around 8 mm, which allows a smaller area to be monitored.
D is incorrect because the amount of light present in the environment does not determine the type of iris that should be used. The iris is determined by whether
the light is fixed (the amount of light in the area is constant) or changes. The amount of light present in the environment helps determine the illumination
requirements that must be met by the CCTV system. Illumination measurements must be taken within the environment itself because characteristics of the
environment, such as exposure to outside light, the paint on the walls, etc., can affect illumination.