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Glossary of CCTV Terms (Page 2)
- COLOR BURST - The portion of a composite video signal that comprises a few cycles of a sine wave of chrominance subcarrier frequency used to establish a reference for demodulating the chrominance signal.
- COMPOSlTE VlDEO - The combined video signal that includes the picture signal, the vertical and horizontal blanking and synchronizing pulses.
- CROSSTALK - An undesired signal that interferes with the desired signal.
- DB (DECIBEL) - A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two signals.
- DC TYPE LENS - An auto-ir
is lens with internal circuit which receives voltage and a video signal from the camera to adjust the iris.
- DEPTH OF FlELD - The front to back zone in a field of view which is in focus in the televised scene. With a greater depth of field, more of the scene, near to far, is in focus. lncreasing the f-stop number increases the depth of field of the lens. Therefore, the lens aperture should be set at the highest f-stop number usable with the available lighting. The better the lighting, the greater the depth of field possible. In other words, the depth of field is the area in front of the camera which remains in focus. The larger the f-number the greater is the depth of field.
- ELECTRONlC SHUTTERlNG - Electronic shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.
- EQUALlZATlON - The process of correcting losses of certain components in a signal.
- EXTENSlON TUBE Kit consis
ting of various size spacers that are used between the lens and the camera to reduce the lens M.O.D. Generally used for very close-up applications. Not recommended for zoom lenses due to loss of tracking.
- F-NUMBER - The f-number indicates the brightness of the image formed by the lens, controlled by the iris. A smaller f-number means a brighter image.
- F-STOP - A term used to indicate the speed of a lens. The smaller the f-number, the greater is the amount of light passing through the lens.
- FlBER OPTlCS - Flexible glass fibers used to conduct energy. It is valuable in the coupling of multi-stage image intensifiers.
- FLANGE BACK - The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount. FOCAL LENGTH - The distance from the cente
r of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. The focal length determines the size of the image and the angle of the field of view seen by the camera through the lens. That is the distance from the center of the lens to the pickup device.
- FOOTCANDLE - It is the light intensity (illumination) of a surface one foot distant from a source of one candela. It is equal to one lumen per square foot. (1 FC = 1 Im ft2). The footcandle is the unit used to measure incident light.
- FRAME - The total area of the picture which is scanned while the picture signal is not blanked.
- FRONT PORCH - The portion of the composite video signal which lies between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding synchronizing pulse.
- GEN-LOCK - A method used to synchronize one or more cameras by external means such as: composite video, composite sync, horizonta
l or vertical sync.
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