CCTV Terminology


Do you want your system to be in Colour or Black & White?
Colour cameras generally require a higher level of lighting than their Black & White counterparts do. Colour cameras give the advantage of being able to easily distinguish and detect objects simply by their colours where Black & White cameras offer better resolution in low light conditions.

Covert cameras. These cameras are so small they cannot be easily seen or are disguised as a different device (such as smoke detector, PIR etc).

Day/Night cameras. These cameras switch from colour to black and white depending on lighting levels. They are ideal for variable lighting conditions.

High-resolution cameras. These cameras have extra light sensors on their digital image sensors. They increase the effective image quality. This type of camera is only effective with high-resolution monitors.

Night Vision cameras. These cameras have their own light source in a light spectrum that can't be seen by the naked eye. These cameras are ideal for small areas with no light.

Outdoor cameras. These cameras have hardened, waterproof outer bodies.

Speed Dome cameras (Pan, Tilt, Zoom) . These cameras allow for remote control of what the camera is pointed at and what it is focused on.

Vandal Proof cameras. These cameras come in hardened cases that can resist the toughest physical abuse.


 

AGC - Auto Gain Control

CCTV Camera automatically adjusts video signal in low light conditions. This can introduce 'noise' in the picture give a grainy appearance.

AES - Auto Electronic Shutter

The ability of the CCTV camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

ALC - Automatic Level Control

On AI lenses a manual adjustment also known as Peak/Average, a facility to make the lens respond more to the highlights (Peak), or more to the darker scenes (Average) , providing a user adjustment of information seen in the highlight.

BLC -  Back Light Compensation

Available on newer CCD cameras which electronically compensates for high background lighting to give detail which would normally appear dark against backgroud light

CCD - Charge Couple Device

CCTV security cameras produce images using CMOS or CCD (Charge Couple Device) chips. CCD chips are higher quality and produce a better image than CMOS.

First invented in the 1970s, this technology uses a shift register combined with photodiodes to create the modern day imaging device. Used in cameras, scanners, fax machines, etc. The size of the CCD chip is normally 1/4", 1/3" or 1/2". As a rule of thumb, the larger the size, the higher the quality of the image produced and the higher the price. However some of the higher density 1/4" and 1/3" CCD chips can now produce as good an image as many of the 1/3" or 1/2" chips

Chrominance

The part of a video signal that contains all of the colour information.

Composite Video

The combination of all electronic information required to produce a video signal. Comprising 0.7 volts video and 0.3 volts sync., hence the term one volt peak to peak.

CMOS

Complimentary Metal Oxide Semiconductor ­ Solid state switching device, also used as a camera pick up device ­ MOS chip.

C-Mount

Industry standard thread mouting portion on the rear of a lens. Note a C-mount lens can be used on a CS mount camera with a 5mm adaptor ring, however a CS-mount lens cannot be used on a C mount format camera.

CS to C Mount Adaptor

A spacer ring of 5mm that allows the use of C mount lenses on CS mount cameras.

CS Mount

Uses the same thread as C mount but requires the lens to be 5mm closer to the image sensor, new industry standard for lens mounting.

Resolution Definiton

The ability of a camera or monitor to resolve fine detail, measured in lines. (Also see TVL)

Electronic Shutter

Compensates for moderate light changes in indoor applications without the use of auto iris lenses.

Electronic IRIS

A feature of modern CCD cameras where the camera electronics automatically varies the shutter to mimic an AI (auto Iris) lens, allowing the use of fixed or manual iris lenses in a wider range of areas.

Horizontal Resolution (TVL)

Horizontal Resolution of CCTV Camera is measured in TV lines (TVL). In simple terms, it defines the picture quality but this depended quality
of camera, lens, transmission and Monitor.

Infrared

The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately 0.7 m) and the shortest microwaves (approximately 0.1 mm).

Infrared Camera

Infrared cameras (or night vision cameras) have special infrared lights installed around the perimeter of the camera lens. This provides special light that the camera uses to capture a good picture even in total darkness.

IR Lighting - Lighting that is above the visible wavelength, used for discrete  illumination in CCTV systems.
IR Shift - Difference in focus of a camera's field of view between white and IR lighting.

IP Rating

A rating used to provide an index of protection from elements such as water and dust ingress

Luminance

Measurement of light in lumens per square metre, the unit of which is lux.

Low Light

Low light refers to the ability of a camera to fuction in low light conditions. The lower the rating, the better it can fuction in low light
conditions. Low lights camera do need some light to produce results. In zero light conditions you will need an infrared (IR) camera.

Lux

Refers to the amount of light required for a camera to capture a good image. Infrared cameras have very low lux.

Power Source (Input voltage)

Power source should be located close to the camera where ever possible. It is normal practice to use:

  • 12V DC for cameras that are installed Indoor and are within a few meters of power source. These cameras usually have DC Jacks
    to accept DC power plugs.
  • 24V AC for cameras that are installed Outdoor or at a distance from monitoring point (upto 135 meters). These cameras usually have screw type connectors.
  • 240V AC for cameras that are installed Outdoor. These cameras suppiled with mains lead that needs termination at a fused switch. Wiring must comply with IEE Regulations.

Resolution

The amount of resolvable detail in the horizontal direction in a picture. It is usually expressed as the number of distinct vertical lines, alternately black and white, which can be seen in a distance equal to picture height.

In other words, it refers to how much detail can be captured on a camera or displayed on a monitor. Cameras typically capture about 380 horizontal lines of resolution. High resolution cameras may capture 450 lines of resolution or more. The higher the resolution, the more detail that can be captured in a picture. The monitors and recording devices can generally handle at least as much resolution as the cameras can capture.

Signal to Noise ratio

The ratio of maximum peak to peak signal voltage to the RMS voltage of the noise at a given time, measured in decibels.

This number represents how much signal noise the camera can tolerate and still provide a good picture. The higher the number the better.

btw, Noise appears on screen as graininess or 'snow' effects on a video image.

Vari-focal Camera

A camera lens in which the focus is not fixed, it can be manually or automatically adjusted.

White Balance

Used in colour CCD cameras. White should be referenced and determined by colour temperature for the truest colour rendition.

White Level

The brighest part of a picture corresponding to 1V peak to peak (0.7V above black level).

Y/C Video signal

Y/C Video signal containing separate luminance (Y) and chrominance (C) to provide greatly improved picture quality from VCR's ie. S-VHS.

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