CCTV Glossary
In order to choose the best CCTV Security System and CCTV Cameras you need to understand some of the basic terminology. Below is a glossary of CCTV terms to help you choose your Surveillance system and CCTV Cameras and CCTV Lenses.
Aperture
Aperture is the area of the camera lens that gathers light. The Iris of the cctv lens controls the size of aperture.
Auto Iris
Auto Iris Lenses adjust for changing light conditions in a camera view. If the sun shines on a camera with an auto iris lens, the lens will adjust the amount of light so the picture remains clear.
CCD
Charge Coupled Device - a light sensitive imaging device for almost all cameras. Typical sizes for CCTV cameras - 1/2", 1/3", 1/4".
C Mount
Type of screw-on mounting for CCTV Camera Lenses. C Mount lenses need an adapter ring when used with CS Mount camera (see CS Mount).
Compression
Compression Techniques are used in Digital CCTV to reduce the file sizes of recorded video images. Typical compression formats used for video are: MJPEG, MPEG-4 & H.264.
CS Mount
More recent type of mounting for CCTV Camera Lenses. Designed for 1/2", 1/3" 1/4" CCD cameras, CS-Mount is the more common lens mount used today in CCTV cameras.
Day/Night Camera
A camera that is 'Day/Night' means it can capture video in both day and nighttime.
In low light conditions, the Sony Day/Night chipset switches from colour to black & white at night to enhance the picture quality
DSP
Digital Signal Processing - a technique by which video quality can be improved by adjusting parameters of the video signal.
DVR
Digital Video Recorder - CCTV Footage is converted to a digital signal and stored on a PC Hard Disk. This is now the standard CCTV recording practice.
ExView
Sony Chipset type that offers very good images in both day and night time. Typically, cameras with Ex-View chipset have good Low Light (LUX) levels.
FStop
The Ratio of Focal Length to the diameter of the lens. The smaller the F-Stop number, the more light is passed.
Field Of View
The view of the camera - in relation to the angle of view and distance of the object from the lens.
Frame
A frame consists of 2 interlaces fields. 25 Frames are created every second
Frame Rate
The quality of a Digital Surveillance Systems is often determined by the Total Frame Rate it can record at. The higher the Frame Rate, the higher the quality of recording and the more Real Time your CCTV recording will be - Real Time recording for 1 camera is 25 Frames Per Second (PAL).
IP Rating
Ingress Protection Scale - 2 numbers indicating the protection level of an outside enclsure - e.g. IP68
IR Cut Filter
An IR Cut Filter is an extra filter inside the camera that moves behind the camera lens when it gets dark. A camera with an IR Cut Filter will produce very high quality images in low light conditions.
Iris
Device inside a lens which opens and closes as light conditions change which adjusts the amount of light passed
JPEG
Joint Photographic Experts Group - an image compression technique used for still images
Luminance
The brightness of a video signal
LUX
Used to specify how sensitive cameras are to light (measured in lumens/sq metre).
e.g a camera with a LUX Level of 0 can see in pitch black. The lower the LUX Level the better the camera will see in the dark.
Motion Detection
Recording method for digital surveillance systems. When someone walks in front of a camera, the pixels change and the DVR defines this as motion. The surveillance system will then record these images to the hard disk. This is a popular recording setup as every event recorded is actually motion driven as opposed to a static image if the system was set to record 'round-the-clock'.
MPEG
Motion Picture Experts Group - a video compression technique for video images
MPEG-4 has fast become the Digital CCTV standard recording compression format.
MPEG-2 is used for DVD Recording quality.
Multiplexer
A Multi Screen CCTV device that allows input of 4, 9, 16 etc cameras and provides a 'Mutli-Plexed' (or split screen) display of those cameras
Noise
Video Signal interference that usually appears as graininess or snow on the picture.
PAL
Phase Alternate Line - Video encoding standard for Europe.
PTZ
Pan Tilt Zoom - a camera which can be controlled via Joystick or DVR and moved up/down, left/right and zoomed in/out.
Peak to peak
Video Signal measurement from the base of the Sync pulse to the top of the white level. A full video signal should be one volt.
Quad Splitter
A CCTV device used to display 4 cameras on one monitor.
Resolution
The number of horizontal lines a system can display.
Digital Resolution (e.g. 720 x 576)
720 = number of points in each row that make up the picture
576 = number of rows
RG59
A type of CCTV Coaxial cable used to transmit cctv camera video signals to a CCTV System.
Sensitivity
The sensitivity of a camera is often configured on your digital surveillance system.
Motion Detection based recording uses relies on the sensitivity of the cameras to trigger recording
Telemetry
Control of PTZ cameras is provided using Telemetry Control. This signal is sent down 'twisted pair' cable or along the same coaxial cable the video signal is being sent down. Typical Telemetry signals are RS-485 or RS-422.
Varifocal Lens
A cctv camera lens whose focal length / viewing angle can be manually adjusted to suit the camera view required.
Typical Vari Focal lens lengths are: 2.5mm-10mm, 3.5mm-8mm, 5mm-50mm
Video Splitter
CCTV device that splits the video signal from a camera (or cameras) so it can be used more than once.
Zoom Lens
A lens which has variable focal lengths. The image can be 'zoomed' in or out whilst the view of the camera remains in focus.