Glossary
This directory provides definitions and explanations for video surveillance industry terms.
A
Adaptive Contrast Enhancement (ACE)
ACE works to increase contrast locally, and brings out image details to produce crisp, highly-detailed images.
Angle of View
May be expressed in Diagonal, Horizontal or Vertical. Smaller focal lengths give a wider angle of view.
Aperture
The opening of the lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment.
Aspect Ratio
The ratio of width to height for the frame of the televised picture. 4:3 for standard systems
Auto Back Focus
The camera automatically and seamlessly allows users to adjust focus of images, enabling quick and easy installation.
Auto Iris Lens
A lens with an electronically controlled iris, allowing the lens to maintain one light level throughout varying light conditions.
Auto White Balance (AGC)
The ability of a color camera to automatically balance flushes of white light into the aperture.
Automatic Gain Control (AGC)
A function on the camera (and many electronics) that automatically balances the gain, or volume, of the signal, with the ability to raise the volume if it is too low and lower it if too high.
B
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. An important adjustment when a zoom lens is fitted.
BLC (Back Light Compensation)
A feature of modern CCD cameras, which electronically compensates for high background lighting, to give details that would normally be silhouetted.
BNC
BNC (British Naval Connector) is a connector used between coaxial cable and an input/output port, either male or female, in CCTV installations.
C
CCD Image Sensor
A light-sensitive imaging device that’s available in many network IP video cameras. The CCD image sensor transforms light into electronic signals and provides strong light sensitivity, to capture video in low light conditions.
CCIR
Determines how many cameras can be recorded at one time. For example, a four-channel DVR allows you to record and view up to 4 video cameras simultaneously.
C-Mount
An industry standard for mounting a lens to a camera with a 1 in x 32 thread and a distance from the image plane of 17.52 mm from the shoulder of the lens. A C-mount lens may be used with a CS-mount camera with a 5 mm adapter ring.
CS-Mount
An industry standard for mounting a lens to a camera with a 1 in x 32 thread and a distance from the image plane of 12.52 mm from the shoulder of the lens. A CS-mount lens may not be used on a C-mount camera.
Coaxial Cable
A type of cable capable of passing a wide range of frequencies with very low signal loss.
Compression
The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal.
D
D1 Pixel
Full resolution that displays 720 x 480 pixels (NTSC) / 720 x 576 pixels (PAL).
Depth of Field
The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus.
Distortion
The deviation of the received signal waveform from that of the original transmitted waveform.
E
EIA
Electronic Industries Alliance. Monochrome video signal standard used in North America and Japan: 525 lines 60Hz
F
F-Number / F-Stop
Indicates the brightness of the image formed by the lens, controlled by the iris. The smaller the F-number the brighter the image.
Field of View
The horizontal or vertical scene size at a given length from the camera to the subject.
Fixed Lens
A fixed focal lens does not allow the FOV to be adjusted; the camera's focal length is permanently set.
Focal Length
The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite position. The focal length determines the size of the image and angle of field of view seen by the camera through the lens. This is the center of the lens to the image pickup device.
Frame Rate
The number of frames per second that the camera produces.
G
Gain
An increase in voltage or power, usually expressed in dB.
H
H.264 Compression
H.264 is a stable, proven and widely used compression technology, with unbeatable recording picture quality and a small compression ratio that saves valuable hard drive storage space (5-10 times smaller than MPEG-4).
HD-SDI
HD-SDI technology delivers high quality live HD video over coax with exceptional resolution and image detail. HD-SDI technology delivers image quality that is far superior to analog CCTV and provides a cost-effective video surveillance solution that's easy to install and integrate with existing CCTV systems.
HDMI Output
HDMI supports standard, enhanced or HD video. Some DVRs feature an HDMI output which delivers enhanced image clarity with crisp images and enables you to view your security camera video in HD on your HDTV screen. HD images can be reproduced with the HDMI support for HD display.
I
IR (Infrared)
IR cameras feature built-in illuminators that project infrared light, which is nearly invisible to the human eye but very visible to IR surveillance cameras. This technology allows you to capture crystal clear, black and white video of suspects who feel protected by complete darkness.
Iris
Mechanism within a lens to regulate the amount of light that passes through, and falls upon, the image sensor. It can be controlled manually or automatically.
J
JPEG
JPEG is a method of compression for photographic images. The amount of compression can be controlled to allow for a tradeoff between image quality and file size. JPEG is the most commonly used format for storing and sending images over the internet.
L
Lens
A transparent optical component consisting of one or more pieces of optical glass with surfaces curved (usually spherical), so that they converge or diverge the transmitted rays of an object, forming a real or virtual image of that object.
M
Megapixel
Pixels are used as a unit of measure. In the security industry, it’s a measure of resolution. Mega refers to 1 million, therefore, megapixel means one million pixels. If you have a 2.0 megapixel camera, in actuality you have a 2 million pixel camera.
Monochrome
Black and white with all shades of gray.
Motion Detection
A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area.
MPEG-4
Moving Picture Experts Group, version 4. A form of compression that makes transmission and storage of images easier.
N
Network IP Camera
An IP (internet protocol) or network IP camera captures and transmits live and recorded video images directly over a network. A network camera requires a high speed internet connection, router, Ethernet cable and IP address to function, and it plugs directly into your network router and transmits data through the network.
NTSC
National Television Standards Committee. Color Video Signal standard used in North American and Japanese: 525 Lines, 60Hz.
O
On-screen display (OSD)
An on-screen display (OSD) is an image superimposed on a screen picture, commonly used by modern television sets, VCRs, and DVD players to display information such as volume, channel, and time.
P
Pan & Tilt
A device that can be remotely controlled to provide both vertical and horizontal movement for a camera.
PTZ
A pan-tilt-zoom (PTZ) camera is a camera that is capable of remote directional and zoom control.
R
Real-Time Clock
A real-time clock (RTC) is an electronic device (most often in the form of an integrated circuit) that measures the passage of time
S
Sensitivity
For a camera usually specified in lux to provide indication of light level required to gain a full video signal from the camera.
SNR or S/N (Signal-to-noise ratio)
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.
U
UPS (Uninterruptible Power Supply)
A battery, attached to a piece of hardware, for example a server, that provides back up power for conducting an orderly shutdown if the server's normal power supply fails.
V
Varifocal Lens
A varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to a parfocal ("true") zoom lens, which remains in focus as the lens zooms (focal length and magnification change).
Video Compression
Video compression is a process during which a video stream is analyzed and unnecessary parts of the data are discarded in order to make a large video file smaller in size.
W
Wide Dynamic Range (WDR)
Wide dynamic range (WDR) is a term used in the surveillance-camera industry to refer to high-dynamic-range imaging.