Terms in CCTV

1.Aperture - The light gathering area of a lens, controlled by the iris.
Automatic gain control (AGC) - A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation and increase the video signal in low light conditions. This usually introduces noise in the picture giving a grainy appearance. Camera specifications must always have AGC off.
2.Automatic Iris (AI) - A lens that takes a video signal reference from the camera. It uses this in an amplifier to derive a DC voltage to open or close the iris aperture. The video level control is part of the lens.
Auto White Balance - A system for detecting errors in color balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.
3.Back Focus - A mechanical adjustment in a camera that moves the imaging device relative to the lens to compensate for different back focal lengths of lenses. This is important when a zoom lens is fitted.
4.Back Light Compensation (BLC) - An electronic feature to allow viewing of highlighted scenes that would normally be silhouetted, thus providing more detail
5.BNC - Standard connector in CCTV for transmitting a basic bandwidth video signal over a coaxial cable.
6.C-mount - The standard screw mounting for 2/3 inch and 1 inch camera lenses. The distance from the flange surface to the focal point is 17.526mm. A C-mount lens can be used on a camera with a CS-mount by adding an adapter ring to reduce this distance to 12.5mm.
7.CCD - Charge coupled device - It is light sensitive and forms the imaging device of most modern cameras. Size is measured diagonally and can be 1/3 inch, 1/2 inch, or 2/3 inch. There are two types, frame transfer and interline transfer.
8.Composite video - The complete video signal comprising the sync and video information. The sync pulse should be 0.3 volts and the video signal should be 0.7 volts.
9.Field of View - Is the height and width of the view that can be seen through a lens.
10.F-Stop - The ratio between the focal length of the lens and the effective diameter of the iris opening. It indicates the light gathering ability of the lens. The small the 'f' stop, the more light is passed. The 'f' stop directly affects the depth of field.