SD CCTV camera technology

One of the advantages of using analogue CCTV cameras is the large range of features and technologies available on even basic camera models. This flexibility means we can find the right security camera specifically suited for each area of your installation, even if that means dealing with difficult lighting conditions or specific requirements.

Some of the technological features available with analogue surveillance cameras include:

Infrared CCTV cameras

analogue CCTV cameraThe level of light a security camera needs to capture a good picture is referred to as the camera’s lux and the lower the lux the better a camera can see in low light. For example a camera with 0.002 lux will see better in low than a camera with 0.3 lux.

Infrared surveillance cameras can operate in what is called ‘zero lux’ conditions or in other words, where there is no light, such as at night. These cameras all have small LEDs that transmit infrared light out around the camera lens lighting up the area and allowing the camera to record in the dark. Infrared light is invisible to the human eye but not to the camera. The distance the camera can “see”, or its night vision range, depends on the number of LEDs it has.

Infrared CCTV cameras will record in colour during the day and then once the light drops below a minimum level they will switch to black & white (monochrome) recording. They will then switch back to colour once the light level increases.

Infrared CCTV cameras come in a number of different styles with different lenses and night vision ranges.

True day/night CCTV cameras

While standard infrared security cameras work well for most standard applications what is recorded is limited by how much of the surroundings is illuminated by the camera’s LEDs, plus the quality of the picture can be comprised.

See the difference in the image from a true day/night or low lux CCTV camera

Surveillance cameras with what is called true day/night technology can automatically gauge light levels and switch between recording in colour or black & white depending on what will provide a better picture quality. Because our largely suburban environments are rarely completely dark, the camera maximises the illumination it can get from the ambient light in the environment essentially allowing it to “see” in the dark. This is combined with a number of performance enhancing features such as noise reduction and image stablisation to provide quality images even in challenging lighting conditions. True day/night CCTV cameras are ideal for securing areas like large carparks or retail premises that are not lit up at night.

Mechanical IR cut filters

Another feature associated with the true day/night type cameras is a mechanical IR cut filter. This is a light filter that is physically removed from in front of the image sensor at night to let in more ambient IR light allowing the camera to better see in the dark. The csecurity ameras light level sensor will trigger a small actuator inside the camera to remove the IR filter at night and replace it when the light level increases. Due to the extra moving parts this feature is usually limited to higher end cameras.

Wide dynamic range CCTV cameras

The difference in image between a Wide Dynamic Range WDR CCTV camera and a standard analog camera

CCTV cameras with wide dynamic range (WDR) are designed to cope with difficult lighting conditions. One of the most common situations this technology is used for is when the security camera is facing into the light. Normal CCTV cameras would only see a dark silhouette when a person emerges from an entrance door or is standing in front of a window. WDR cameras can differentiate between light levels as though each pixel has its own auto-iris allowing it to see faces or details a normal camera could not.

CCTV cameras with wide dynamic range (WDR) are designed to cope with difficult lighting conditions. One of the most common situations this technology is used for is when the security camera is facing into the light. Normal CCTV cameras would only see a dark silhouette when a person emerges from an entrance door or is standing in front of a window. WDR cameras can differentiate between light levels as though each pixel has its own auto-iris allowing it to see faces or details a normal camera could not.

Numberplate capture CCTV cameras

Vehicle licence plates are very difficult to capture with traditional surveillance systems using standard analog surveillance cameras and a DVR.

There are several reasons why rego plates are difficult to capture on normal (analogue) CCTV systems:

The recording resolution of an analogue DVR is low – a 4CIF/D1 recording resolution is only around 0.3 megapixel. In order for an analogue DVR to record a number plate on a moving vehicle the camera needs to be really close to the subject (or the camera must have a long zoom lens) and the front or rear of the vehicle must fill at least half the picture. This is simply not practical for most environments. A number plate capture camera addresses this problem by digitally processing the image to sharpen up the lettering on the number plate. Number plate cameras also have a maximum distance for operation as specified by the manufacturers. This maximum distance is determined by the lens fitted to the camera and also the IR illuminators power output (see below). This allows us to accurately position the camera to ensure the best possible results.

Compare the image from a standard analog and number plate capture CCTV camera

New Zealand vehicle licence plates are very reflective. This means most standard cameras flare out when the sun hits the plate, or at night when the vehicle’s headlights are on, or the infrared (IR) from the camera’s illuminator reflects off the number plate. Number plate capture cameras are tuned to the specific reflectance of the plate they are designed to capture. This reduces the glare during the day and at night causes the number plate to “pop” out of the picture. Note: the downside of this is that the rest of the image is very dark so if you need to record the make/model of cars at night a second camera will be needed in the same location. During the day the number plate camera works just like a normal colour camera.

Headlight glare is another primary reason standard surveillance cameras struggle to capture licence plates at night. As the vehicle approaches the camera with its’ head lights on a standard camera will flare out making it impossible to read the number plate or even tell the make/model of vehicle (see the comparison images).

Note: for clients where numberplate capture is important we would recommend an IP based system such as the Hikvision ANPR (Automatic Numberplate Recognition) software.

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