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Glossary of CCTV Terms
- ANGLE OF VlEW - The angular range that can be focused within the image size. Small focal lengths give a wide angle of view, and large focal lengths give a narrow field of view.
- APERTURE - The opening of a lens which controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment. By increasing the f stop number (f1.4, f1.8, f2.8, etc.) less light is permitted to pass to the pickup device.
- ASPECT RATlO - The ratio of the picture frame width to the picture frame height in standard TV systems. It is 4 units horizontal over 3 units vertical.
- AUTOMATlC FREQUENCY CONTROL (AFC)An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.
- AUTOMATlC GAlN CONTROL (AGC)- An electronic circuit used by which the gain of a signal is automatically adjusted as a function of its input or other specified parameter.
- AUTOMATlC lRlS LENS - A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device.
- ATTENUATlON - A decrease or loss in a signal.
- BACK FOCAL DlSTANCE The distance from the rear most portion of the lens to the image plane.
- BLACK LEVEL - The level of the video signal that corresponds to the maximum limits of the black areas of the picture.
- BLANKlNG - The process of cutting off the electron beam in a camera pickup device or picture tube during the retrace period. It is a signal that is composed of recurrent pulses at line and field frequencies. It is intended primarily to make the retrace on a pickup device or picture tube invisible.
- BLOOMlNG - The halation and defocusing effect that occurs around the bright areas of the picture (highlight) whenever there is an increase in the brightness intensity.
- BRlDGlNG - A term indicating that a high impedance video line is paralleled, usually through a switch, to a source of video.
- "C1' MOUNT/"CS" MOUNT - CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. Many of today's cameras can accept either type of lens, but it is important to make sure that camera and lens are compatible and set up properly. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. Your picture will be out of focus if you use a CS-mount lens on a C-m
ount camera.
- CANDLEPOWER - The unit measure of an incident light.
- CCTV - The common abbreviation for Closed Circuit Television.
- COATlNGS - Light is lost by reflection from optical surfaces that are intended to be refractors only. This loss is effectively reduced by very thin coatings on the lens surfaces. This can be seen as a blue or violet hue on the lens surface.
- COAXlAL CABLE - A type of cable capable of passing a range of frequencies with low loss. It consists of a hollow metallic shield in which one or more center conductors are put in place and isolated from one another and from the shield.
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