IP Network Cameras
Network cameras have now developed to a high performance capability that allows them to compete with or even exceed the performance of traditional analogue CCTV cameras.
Traditionally we have measured the resolution of analogue CCTV cameras in TeleVision Lines (TVL). This measure counts the number of vertical lines that can be resolved across the screen. Due to limitations of the PAL video standard an effective top limit of about 540TVL has been reached.
Sanyo introduced a 520TVL highresolution colour camera about five years ago. Sony pipped this with a 530TVL model, Bosch and a few others have now produced 540TVL cameras. This rate of progress, over that period of time, illustrates well that even the best manufacturers have reached a plateau in terms of what it is possible to deliver from a traditional analogue PAL CCTV camera.
IP cameras, in common with most products such as computer monitors and digital still cameras from the IT sector, express their image resolution in pixels.
520TVL equates to 752 X 582 pixels.
Megapixel IP cameras are now quite commonly delivering 1280 X 1024 pixels.
Simply multiply the two numbers to express the resolution in megapixels e.g. 1280 X 1024 = 1.31 megapixels.
Two, three and five megapixel cameras have quickly become available, and plainly can deliver much greater image detail than traditional analogue CCTV cameras.
There are already IP cameras capable of delivering 16 or even 21 megapixel images. These cameras can deliver images of whole street scenes for recording. There is so much resolution within those images that the recordings can be expanded to reveal facial identity after an event.
Early network cameras did not perform well in low-light conditions, and in their effort to perform would ‘drop frames’ in low light conditions, resulting in poor quality jerky video.
The latest IP cameras are now rated down to well below 1 lux and are fully compatible with auto-iris lenses to utilise all of the available light. They now provide full frame rate (25 frames per second) under all conditions.
As the name suggests, network cameras connect directly to your existing site network.
Many new buildings are ‘flood cabled’ with network points from new, meaning that typically the required camera location is never far from an existing network point.
Network bandwidth has always been a concern, with many IT managers worried that adding video to their networks would cause a significant detrimental impact upon network performance. However, most premises now have gigabit networks which can usually cope well with the additional load of networked video.
Alternatively, as the gigabit network switches are relatively cheap, it is quite simple to patch data cables to create a separate and dedicated network for video.
Of course, traditional analogue CCTV requires co-axial or other dedicated video transmission cabling, and therefore dedicated cables must be installed from the camera to the monitors and recording devices.
Power over Ethernet (POE)
Most network cameras can be fed with their power via the same network cable that will carry the video data back to the network. Truly a single cable low-voltage installation; often an existing data network cable.
Recent developments now allow for higher power devices such as pan, tilt, zoom cameras and lights to be fed via POE. Even external camera housing heaters can now be fed via POE.
Traditional analogue CCTV cameras would normally require an electrician to provide an adjacent mains supply, or at the very least to be fed power separately via a second low-voltage supply cable.
Data over cat5 cable has a transmission distance limitation of 100m, however devices are now available which can simply be inserted in the line and boost this for another 100m. Several devices can be added in a daisy-chain manner to achieve an extra network reach of 500m.
Furthermore, these booster devices are POE compatible, maintaining the strategy of needing only one cable to add a camera hundreds of metres beyond the existing reach of your network.
Dedicated point-to-point wireless video links for analogue CCTV cameras remain relatively expensive. Typically, only one video signal would be transmitted over one link. Additionally, if telemetry control of PTZ cameras is required, a second separate wireless data link (radio modem) is necessary.
Wireless LAN on the other hand is readily available, devices for the domestic market are capable of links of 100m or more, and the single link will carry both video and data, and can cope with several cameras at once.
Indeed, this capability has now been scaled-up to wireless mesh networks covering whole cities with many cameras linked back to a central control room, and even allowing Police Officers live video access via hand-held terminals on foot in the city.
Evidently network cameras and IP CCTV has now come of age and potentially offers some real benefits over traditional CCTV solutions.