This site explains the use of CCTV in both the home and commercial applications. There are handy calculators, suggestions and detailed explanations from an industry expert.
Index
CCTV Cameras
WHY WE NEED CCTV
We live in a world where crime is ever present and thieves will take any opportunity to help themselves to your new expensive racing bike or your state of the art laptop.
CCTV captured footage will allow Police to possibly recognize the offenders and in some cases return your belongings. It also prevents the repeat offenders.
THE BASICS OF CCTV
Choosing the specifications for your CCTV system can be a little daunting and complex. We will start with the basic types of CCTV systems:
ANALOGUE CCTV
In a analogue CCTV system the signal it uses is a continuously variable voltage.
An analogue CCTV system is one based on the old TV systems that used either the PAL or NTSC format. These systems where not 'digitised' in anyway and where susceptible to video 'noise' and restricted in resolution (sharpness). The restriction was because the maximum number of vertical lines was 625 in the case of the PAL format.
Analogue systems have the benefit of being easy to set-up, I.E no IP address to worry about. Plus compatibility is not a problem as long as you mix a PAL camera with a PAL recorder.
Since PAL and NTSC standards are country specific , this usually is not a problem.
PAL??? > Phase alternating line. The standard uses 625 vertical lines and a refresh rate of 50HZ
IP CCTV System
In an IP CCTV systems the signal is digital through-out where the voltage levels represent Zero and ones.
IP systems usually results in much high quality images, flexibility and low video noise, (as long as compression is kept to a minimum).
Resolution in an IP system can be high because it does not have to adhere to a standard such as PAL or NTSC and hence vertical resolution can be 720p, 1080p and more.
720p ??? >> This indicates the number of horizontal lines in the image and the p indicates that the lines are progressively scanned from top to bottom of the screen. In a analogue systems, it uses two interlaced fields.
Aspect ratio is important in video and the two common aspect ratios are 4:3 and 16:9.
4:3 offers a more square shaped image, whereas 16:9 is the letterbox image, which is more natural to the eye.
You can use either one. My preference in CCTV applications is 4:3 as its not cropped top and bottom and you can get more in the image of the subject.
Compression is vital in an IP video system as the base video signal without compression results in a very large file, to large for transmission or effective storage. Compression is usually H.264, with H.265 now becoming popular. The compression works by only encoding the data which was different to the last scene. The compression algorithm for a person walking across a car-park would only encode the movement of the person. The stationary cars would only be encoded once then the frames after that would be duplicated for that part of the scene.
Compression, resolution and images per second (ips) determine the bit rate of a camera, this then in turn impacts on how much storage you will get on your IP Video recorder.
For example a camera with a bit rate of 2Mbs recording on a 1TB HDD will give you approximately 46 days.
These factors must be considered carefully as too much compression (I.E) allowing too little bit rate for the resolution and ips will result in pixelated images.
Lower ips will give greater storage because bit rate it lower, but may not catch the movement you need. In general unless you need to see fast moving object my preference is 10ips.
Setup in a IP video system is a little more complicated than a analogue system. The camera has to have an unique IP address and an Ethernet switch has too be used. The Ethernet switch can be PoE, which actually powers the camera, hence video signal and power is all down one cable. Luckily many IP Video recorders have a wizard which automatically recognises the camera then assigns and IP address, making set up easier. Then resolution and compression can also be setup.
PoE ??? >> Power over Ethernet
CCTV cameras
Cameras can be of various types below are the common camera types. Manufacture selection is, 'you get what you pay for'. If you choose brands such as Panasonic, then you can be assured of good quality video and longevity of the product.
Box camera: This is a camera that requires a camera housing if used outdoors and usually does not include a lens. The lens is chosen dependent on the scene you are covering, more about this later.
Vari-focal dome camera: This is a camera in its own housing rated for either indoor or outdoor. The housing is dome shaped (hence the name). It also has a lens that can be zoomed in and out to suit the scene you are covering.
The Vari-focal dome camera has the advantage that you don't need to add a lens or housing. But you may be limited in lens sizes, which is where the box camera is used. Note: Some dome camera are not vari-focal and instead have a fixed focal length. You need to be sure the focal length covers the scene you are after.
360degree cameras: As the name suggests these dome cameras cover a 360degree field of view. They are great for capturing a complete foyer, for example. But must be treated an overview camera as facial recognition may be hard to discern.
Pan tilt zoom cameras: Pan tilt zoom cameras (PTZ) allow you to move the camera around, panning left and right plus up and down. You can also zoom in, out and focus. Preset positions can also be set, where the camera remembers a position which can be recalled immediately. PTZ's are usually (but not always) a dome type format. PTZ are great in that you can view a scene then zoom into an object for clarity. You can usually set up the PTZ so it will conduct a tour of a scene moving from one preset position to the next.
But of course there is an associated cost with PTZ being more than a box or dome camera.
Lens Selection
There are various factors to consider for lens selection:
Focal length: this determines the zoom factor of the lens and how much area the lens will cover
F-Stop: The F stop determines how 'fast' the lens is. A lower F stop transmits more light to the camera. Essential in low -light conditions.
CS or C mount fitting: Older box camera used a C mount fitting. You can add a C mount lens to a CS mount box camera but an adaptor must be used or the camera will be out of focus.
Auto Iris: An auto iris lens changes the iris setting of the lens dependent on the amount of light. A fixed Iris lens has only one iris setting. The camera must then attenuate the light it receives electronically.
To determine the view you want you must calculate the focal length of the lens. To do this you need to know:
A. The distanced from camera to subject
B. The horizontal distance of the area you want to see at that distance.
C: Is the camera you are using a 1/2", 1/3" or 1/4" sensor. In these examples we will assume 1/3" which is the common sensor size.
Lens Wheel
CCTV LENS CALCULATOR
Enter Distance to subject
Enter width of scene
1/3" Result =
1/4" Result =
CCTV STORAGE REQUIREMENTS
For an analogue system, storage requirements are based on ips (images per second), field or frame recording and the compression used. All these parameters are set at the DVR (Digital Video recorder).
For a digital IP system storage is based on the bit rate of the camera which in turn based is on the ips, resolution (1080p, 720p, etc.) and compression.
In each case storage is usually achieved using on-board Hard drives. For extended recording durations a NVR or DVR may support a hard drive (HDD) extension unit. The extension units in many cases support raid 5 or raid 6. For mission critical installations raid is recommended. A raid system will recover lost information on a failed HDD using data from the other HDD.
Calculating storage requirements is an important aspect of designing a CCTV system. Not enough storage and you will not record as many days as you hoped for.
Below is a IP system storage calculator which calculates how much storage your NVR will need based on the number of cameras and number of days. It assumes H264 recording with a bit rate of 2046kbs for 720p recording 4096kbs for 1080p. Its not camera manufacture specific but should give you a general idea on storage requirements.
bit rate 2046kbs??? >> This bit rate will give you 30ips with a resolution of 720p
bit rate 4096kbs??? >> This bit rate will give you 30ips with a resolution of 1080p
CCTV STORAGE CALCULATOR
Enter number cameras
Enter number of days
720p Result =
1080p Result =
Installation
Good Installation is key to providing optimum video quality and to ensure no hardware problems occur in the future such as water intrusion. The following are tips on both a IP and a analogue installation.
Camera mounting
Surface mount: This is simply installing the camera flat against the ceiling. Cables and conduit are run into the side of the camera in the case of a concrete ceiling.
Recess mount: The camera is recessed into the ceiling, usually a ceiling tile with a special mounting kit (normally optional). Recessing gives a less obtrusive installation, whereby only the dome can be seen.
Wall mount: Camera is mounted on a wall bracket.
Pedestal mount: A PTZ is mounted on top of a pole using a Pedestal mount bracket.
Pole mount: A PTZ is mounted on the side of a pole. Usually used in conjunction with a wall mount bracket. The PTZ is attached to the wall mount bracket. The bracket mounted to the pole mount bracket then band straps pass through the pole mount and around the pole, securing the camera.
Cable and Transmission
For each of the mounting options ensure the cable does not 'encourage' water to flow into the housing, for example a cable running directly down into a housing will cause water to flow into the housing. Running the cable past the camera then loop back up to the camera will cause water to drip of the end of the loop and not into the camera.
Maximum cable lengths and cross sectional area of cable must be correct for the installation
For a analogue installation the coax cable and power cable type must be chosen dependent on cable length. Failure to do this will cause erratic or none operation of the camera.
Follow all the manufactures recommendations when terminating and sealing the cable. Some manufactures include special sealing tape, ensure you use the tape or problems will arise.
Video coax must have an impedance of 75ohms, ensure you use the correct cable such as those specified below. Choosing a cable with incorrect impendence such as 50ohms will cause video quality issues.
Video coax
RG59U -----> Maximum distance 100mtrs
RG6 ---------> Maximum distance 200mtrs
RG11--------> Maximum distance 250mtrs
Figure 8 power cable
Ethernet cable
CATAGORY 5 UTP ------> Maximum distance 100mtrs @100Mbs (inc PoE)
CATAGORY 5 or 6 UTP--> Maximum distanced 100mtrs @1000Mbs
Ethernet extenders can be used to extend data and PoE beyond these distances.
When terminating the Ethernet cable it is important to adhere to the Ethernet cabling standards. For example the T568A and T568B. Below are the relevant pin-outs.
T568A standard
T568B standard
Connections shown above must be used at both ends of the cable. Failure to do this may cause the camera to continually reboot at it tries to establish a connection.
Once the cable has been terminated always check the cable with a LAN tester, to ensure connectivity.
Fiber cable
For long distances it is necessary to use Fiber cable. There are two types of fiber cable multimode for distances of approximately 3Kms or Single mode for distances greater than 3Kms.
If there are large distances and many patches, the optical budget of the fiber modem must be taken into consideration. If for example the optical budget of the fiber modem is 12db, the fiber cable is 3db/Km and cable is 3Km, then you have 3db spare for patches and terminations. Once the optical budget has been exceeded then operation will not be reliable.
Fiber has many benefits including protection from lighting for sensitive electronic equipment
as the fiber acts as an isolator. Plus signal integrity is maintained in fiber. But note you must have the expertise in terminating a fiber connection, incorrectly terminated fiber can result in optical loss in the connection.
Ethernet Converters
If there is an existing coaxial infrastructure and you wish to convert to IP, you can use Coaxial Ethernet converters. A transmitter has a ethernet output which is connected to a camera and the receiver can be connected to a ethernet switch at the head-end, In between you have the coaxial cable. Distances of 600 meters can be reached plus you can also transmit PoE power to power the camera. But note this does have power limitations.
IOS App Privacy policy
Disclaimer: reasonable effort has been made to ensure that the information provided by this blog and the calculators is accurate, however, no guarantees for accuracy of information is made information is provided "as is", without warranty of any kind, whether expressed or implied.
Focal length: this determines the zoom factor of the lens and how much area the lens will cover
F-Stop: The F stop determines how 'fast' the lens is. A lower F stop transmits more light to the camera. Essential in low -light conditions.
CS or C mount fitting: Older box camera used a C mount fitting. You can add a C mount lens to a CS mount box camera but an adaptor must be used or the camera will be out of focus.
Auto Iris: An auto iris lens changes the iris setting of the lens dependent on the amount of light. A fixed Iris lens has only one iris setting. The camera must then attenuate the light it receives electronically.
Installation
Good Installation is key to providing optimum video quality and to ensure no hardware problems occur in the future such as water intrusion. The following are tips on both a IP and a analogue installation.Camera mounting
Surface mount: This is simply installing the camera flat against the ceiling. Cables and conduit are run into the side of the camera in the case of a concrete ceiling.
Wall mount: Camera is mounted on a wall bracket.
Pedestal mount: A PTZ is mounted on top of a pole using a Pedestal mount bracket.
Pole mount: A PTZ is mounted on the side of a pole. Usually used in conjunction with a wall mount bracket. The PTZ is attached to the wall mount bracket. The bracket mounted to the pole mount bracket then band straps pass through the pole mount and around the pole, securing the camera.
Cable and Transmission
For each of the mounting options ensure the cable does not 'encourage' water to flow into the housing, for example a cable running directly down into a housing will cause water to flow into the housing. Running the cable past the camera then loop back up to the camera will cause water to drip of the end of the loop and not into the camera.Maximum cable lengths and cross sectional area of cable must be correct for the installation
For a analogue installation the coax cable and power cable type must be chosen dependent on cable length. Failure to do this will cause erratic or none operation of the camera.
Follow all the manufactures recommendations when terminating and sealing the cable. Some manufactures include special sealing tape, ensure you use the tape or problems will arise.
Video coax must have an impedance of 75ohms, ensure you use the correct cable such as those specified below. Choosing a cable with incorrect impendence such as 50ohms will cause video quality issues.
Video coax
RG59U -----> Maximum distance 100mtrs
RG6 ---------> Maximum distance 200mtrs
RG11--------> Maximum distance 250mtrs
Figure 8 power cable
Ethernet cable
CATAGORY 5 UTP ------> Maximum distance 100mtrs @100Mbs (inc PoE)
CATAGORY 5 or 6 UTP--> Maximum distanced 100mtrs @1000Mbs
When terminating the Ethernet cable it is important to adhere to the Ethernet cabling standards. For example the T568A and T568B. Below are the relevant pin-outs.
|
| T568A standard |
|
| T568B standard |
Once the cable has been terminated always check the cable with a LAN tester, to ensure connectivity.
Fiber cable
If there are large distances and many patches, the optical budget of the fiber modem must be taken into consideration. If for example the optical budget of the fiber modem is 12db, the fiber cable is 3db/Km and cable is 3Km, then you have 3db spare for patches and terminations. Once the optical budget has been exceeded then operation will not be reliable.
Fiber has many benefits including protection from lighting for sensitive electronic equipment
as the fiber acts as an isolator. Plus signal integrity is maintained in fiber. But note you must have the expertise in terminating a fiber connection, incorrectly terminated fiber can result in optical loss in the connection.
Ethernet Converters
If there is an existing coaxial infrastructure and you wish to convert to IP, you can use Coaxial Ethernet converters. A transmitter has a ethernet output which is connected to a camera and the receiver can be connected to a ethernet switch at the head-end, In between you have the coaxial cable. Distances of 600 meters can be reached plus you can also transmit PoE power to power the camera. But note this does have power limitations.