No CCTV system is cheap, so do not waste money on the wrong system. It should give high quality recordings suitable for identification and use in court, not just a blurred image, together with the correct date and time.
The ideal image will be well lit, as detailed as possible, from a camera at around head height, and not distorted. Unfortunately the camera could be vandalised, so the optimum may be just out of reach, at a minimum height of around 2.5 metres. The best lighting conditions may only occur at a particular time of day, so consider two cameras looking from opposite directions.
Modern cameras may be extremely sensitive, but do not expect the same quality under low light conditions. Reading vehicle number plates will be difficult if it is moving or the vehicle lights are on, so an LED floodlight with passive infra-red PIR detector will help. Some recorders can provide a switched alarm output that could be used to drive a relay.
The two most common shapes, dome and bullet, will probably have identical contents. Most CCTV cameras have a fixed wide-angle lens, giving wide coverage, all in focus, but a usable image only when relatively close. Different lenses may be available, but more expensive and perhaps with smaller apertures. A lens with longer focal length will have a more restricted depth of focus. External housings are available with an integral heater to prevent misting and condensation problems, and may be useful with narrow angle lenses.
Many cameras have infra-red LEDs for night vision, but they are often very close to the lens. The LEDs attract insects, and the insects attract spiders that will spin a web right in front of the lens. You may need to spray the camera with SpiderX. The bullet shape may have a lens hood, but possibly too small to do much without being visible. I have found that a dome camera under an inverted length of Ogee guttering stays cleaner for longer, but although out of view the cover could reflect light from the LEDs and cause fogging under low light conditions, cured using less reflective adhesive tape.
Some cameras can handle a very wide dynamic range WDR of light levels, and can give an acceptable full colour image at very low light levels. Good quality wide aperture lenses can be expensive. There may be a choice of lenses, including remote controlled optical zoom, although some are designed to be manually adjusted and re-focused only on installation. Some also provide automatic or remote control of pan, tilt, and zoom, audio facilities, and may have facial and number plate recognition systems.
Light intensity drops rapidly away from a light source, so consider multiple lights around the area to be covered.
Modern high definition cameras give one or more compressed video streams over ethernet cable, not co-ax, and can run on either separate local power (normally 12 volts DC at the camera), or Power over Ethernet, PoE, which sends a nominal 48 volts DC through the cable. Wireless cameras still require power, although may be able to run on solar power with battery backup.
Cameras often have software that can send their output via the internet if required, and some recorders are happy to receive all the camera outputs via a single network cable, so that the cameras can be connected to and powered using PoE from a network switch in another more convenient location such as a house loft. If a recorder supplies direct PoE to a limited number of cameras then the maximum number of cameras that will be accepted via the network is likely to be the specified total less the number of PoE connectors provided.
The digital compression software can easily perform motion detection at the camera, with sensitivity control and masking to disable selected areas. This can work well, although it may be difficult to ignore reflections and shadows from anything moving outside the enabled areas. About half of my cameras are close to busy roads, with little difference between motion detection and 24/7 continuous recording. The data stream can be delayed in memory for a few seconds, allowing the motion detection signal to start the recording from before the motion was detected, continuing for a timed period after detection ends.
The recorder may be designed to supply PoE to some of the cameras, some may be accepted via an ethernet network, but with absolute limits on the numbers of each, as well as the total, together with the individual and total data rates. A recorder that provides 8 PoE connections with a total maximum 16 cameras may not accept more than 8 cameras via the network. Recorders may claim to work with cameras manufactured by others, but perhaps not under all connection modes, so possibly restricted to network connection only. Remote control software, and remote access to the recorder, are normally provided, but its use may be restricted to specific operating systems. Be aware that almost anything connected to the internet could be a security risk, and possibly used by others to obtain information such as whether premises are likely to be occupied at particular times.
The recording medium has to record the cameras as they are presented. Special surveillance hard discs can cope with heavy loading 24/7, while solid state discs must be able to cope with repeated re-writing. The amount of storage space required will vary according to location. My original 2TB drive would only retain about 3 to 5 days recording before it was over-written, while 1TB might retain recordings for a month in a quiet area where the only movement is due to wild animals and birds, with few rapid lighting changes and little wind blown vegetation. Some cameras can also record to an internal memory, and MicroSD cards specially designed to record high data rates 24/7, with a stated minimum number of repeated over-writes, are available.
I have found that although a recorder may specify a maximum disk capacity, it may work perfectly with a much larger disk that has already been partitioned using GPT and then formatted using the Linux ext4 format, although you may not wish to chance the cost of a very high capacity disk designed to handle 24/7 CCTV.
There are many different types of ethernet cable. CCA means copper coated aluminium which is cheap, but will quickly corrode and fail. The standard cable is designed for internal use only, and should be protected if used outside. External cable is available, but more expensive, as is low smoke, low halogen cable which may be required under local building regulations. Cat5e cable will probably be adequate, although Cat6 cable has thicker conductors and will be suitable for longer lengths and higher future data rates.
A fixed installation will not require the more expensive stranded rather than solid conductors, but ensure that the connectors are designed to match the cable. Insulation displacement connectors only for use with stranded cable may have two offset spikes, but three spikes with alternate offsets are more reliable with solid cored cable.
Ethernet cable is notorious for kinking and snagging, so is normally supplied in a box designed to supply the cable from the centre of the spool. Do not pull the cable from the box until you are ready to pull it straight into position. Make sure that all connections are protected from damp as the contacts can be dissolved if wet while powered. Totally waterproof silicone oil or grease can help protect the cable ends and connectors.
The correct standard cable connections are important but not immediately obvious. A simple tester may show that the correct pins are connected end to end, but they must also have the cable pairs connected via the correct pins.
Standard ethernet connections (pdf file)Return to site index