Surveillance systems technology evolved greatly in the last two decades, and its price dropped significantly to the level of common consumers. HD capable security cameras and the widespread of high storage capacity Digital Video Recorders (DVRs) even opened the door for complete new applications that weren't available before.
Really big quantum leaps in surveillance systems technology just occurred in the last five years, when advanced communication systems combined with new revolutionary technologies like artificial intelligence, cloud storage/computing, Big Data processing and others, which allowed surveillance systems to achieve “science fiction” like tasks that were thought to be impossible before. Now surveillance systems can search thousands of video hours to locate individuals using facial or clothes recognition, identify objects like cars, motorcycles with type or color or even number plates within few seconds! It can also detect and generate alerts for traffic congestion, or even count car numbers passing through major streets to give valuable statistics data to decision makers so they can react in proper time if any incidents occurr, and off course it's not strange to be a vital building block in the Smart City concept.
Although our article is a bit long, but we think it won't be sufficient to cover all surveillance systems details. So we tried to simplify and be concise as much as possible, whether you are professional or casual reader, we hope you find it useful and entertaining.
1- Firstly, what are surveillance systems? and what are its main components?
2- Camera types and specifications.
2.1 Camera (Sensor/lenses) Specifications.
2.2- Security Camera Signal&Connectivity.
2.3 Camera Housings & special Features.
Surveillance systems -also known as CCTV systems- vary greatly in complexity according to application, however any surveillance systems should at least fulfill three essential jobs:
1- Video Capturing: Capturing footage and sending it as a video signal is done by different types of cameras (Analog, HD, Network). Cameras topic will be expanded in details in (2- Camera types and specification) section.
2- Video Recording: the process of storing footage on proper storage media for later retrieval is done by Digital Video Recorders (or DVRs) and it has many types. Also named as Network Video Recorders (NVRs) in case of network based cameras are used. Beside the storage, some DVRs/NVRs types can apply extensive processing on video to extract and categorize its contained information. DVRs/NVRs will be expanded in details in part 2 of this article.
3- Video Replay/Viewing: which is done through simple monitor connected directly to DVR/NVR, or through the internet or any communication link.
In very simple cases, surveillance systems may comprise of one monitor connected directly to one camera for simple instantaneous monitoring without any recording mean,
but in advanced applications there can be hundreds of cameras connected through Fiber optics cables or wirelessly using Microwave, Satellite or mobile network links, and the footage captured is stored and processed by NVR servers with fast GPUs, huge SAN storage capacities and hundreds of remote monitoring points.
Cameras specifications usually overlap and may cause confusion for even technicians, so we will try to simplify the basic concepts behind these specifications and provide as much details as possible, to educate our readers about the proper selection of camera specifications.
Surveillance Cameras specs can be listed under three main Categories:
1- Security Camera (Sensor/lenses) Specifications.
2- Security Camera Signal & Connectivity.
3- Security Camera types & special features.
Sensor/lenses combination directly affects video quality in addition to the connectivity type which we will mention later.
First, lenses collect the light that reflected from scene objects, then it concentrates this light on camera's “sensor surface”, which in turn will convert this “minimized scene” into electrical analog/digital signals -according to camera type- that will be sent to monitor or recording device.
There are two types of technologies used to manufacture camera sensors, and each one has its own pros and cons:
1- Charge Coupled Devices or CCDs: CCDs are known to have highest light sensitivity (.001 lux) among competitor technologies - however this is changing since 2016-, which enables it to capture good quality videos at dark/low light situations, so it's usually used in “Night Vision” cameras, also it has high fidelity for colors. however this technology is expensive due to the complexity of its manufacturing process.
2- Active Pixel Sensor or MOS: comparing to CCDs, it has simpler manufacturing process and cheaper, but unfortunately it has less light sensitivity and even lower capturing quality -noisy pixels- when compared to CCDs. MOS sensors dominated lately after receiving huge investments from smartphone companies, which led to enhancing MOS capabilities with time to the extent that it can be competitive to CCDs in some applications.
Both technologies depends on millions of light sensitive photodiodes, each one of the photodiodes convert a single “light spot” of the image (known as pixel) to an electrical potential relative to the light intensity and wavelength.
This electrical potential is read out and processed by specialized integrated circuit and conditioned to be sent to recording device as an analog digital signal according to camera type.
Camera sensor performance depends on its Resolution and Size, the first is a measure of how many light sensitive photodiodes are available on sensor surface, the more the better as the sensor will be able to describe more pixels which should enhance video clarity, typical resolution unit is megapixel(or simply MP) which means 1 million photodiodes on sensor surface, Sensor Resolution is what determines the max “Video Frame Size” that can be sent by the camera (check the next photo).
However Sensor resolution isn’t the sole parameter in camera quality as some people may think, as Camera Sensor Size -our second sensor performance parameter- has a very vital role in video quality.
Surveillance camera sensors come in many sizes, common sizes- measured diagonally- are ¼”,⅓”,⅔” inches, the rule is the “bigger sensors are more light sensitive and yield clearer video” and this is because that photodiode elements on bigger sensors are bigger in size and can receive more light.
The Size/Resolution pair can make a video taken by a 1.3 MP is more clear and describing more details than a 2.0 MP sensor that is smaller in size, however get sure to check a video sample before you buy.
lenses are described by Focal Length and F-number or aperture size, and if the lenses are fixed or varifocal.
Focal length is measured in millimeters (mm), and it controls the magnification (zooming) of lenses and the Field of view. The rule is “the more Focal length, the more magnification and the less Field of view”
Surveillance Camera lenses can be divided into three types:
1- Fixed or Monofocal lenses: the cheapest and simplest lenses, it has fixed focal length that can not be changed.
2- Varifocal lenses: a little bit expensive than Fixed lenses, its focal length can be manually adjusted as needed to control zooming and field of view.
3- Motorized or Zoom lenses: the most expensive choice and it has a small motor that can move lenses to zoom in and out according to what you need, it’s usually found in PTZ cameras.
Aperture or the F-number is a measure of much light is allowed to pass through the lenses or in other words the lenses brightness, it can be calculated by dividing focal length by lens diameter. The rule is “The smaller aperture or F-number, the greater amount of light that will pass through the lenses”. Smaller F-number is more suitable for dim light conditions, if the F-number is 1.6, it will be written in the form of F/1.6 or 1:1.6 .
Whatever type of Security Cameras you are using, you will need two essential cables:
1- Signal Cable: and it’s usually a coaxial cable (with BNC/RCA connectors) or UTP cable (with RJ-45 connector) or Fiber Optics (using special couplers) for wired cameras.
2- Power Cable: usually 12VDC through simple male/female DC connectors (see next image).
The Signal Cable of the Security camera can carry many types of signals, and it’s usually the signal type that determines whole camera type and capabilities, however cameras can be classified with respect of signal and connectivity into three types as following:
This type of camera uses an analog Composite Video Signal, it may be called CVBS also. The naming comes from the fact that it is a combination of three different signals (luminance, chrominance, sync) in the same cable - usually coaxial one-, it can be adhering to either NTSC or PAL system.
Analog camera resolution is measured using Television lines (TVL) which is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height (see Wikipedia)
The maximum resolution that a traditional analog camera can reach is 700TVL or 960H ( H for horizontal), meaning 960 pixels can be counted in the horizontal span.
Some Security camera Vendors may write figures bigger than 700TVL for cvbs cameras, but this is typically unreal, or they just mean that it’s an HD camera that has a resolution that is “equivalent” to this figure.
Traditional analog security cameras is known to be the cheapest among all choices, but it’s video quality is very bad comparing to Analog Cameras with (HD over Coax) technology. cvbs signal strength is weakened and video quality may degrade significantly if coaxial cable is longer than about 150m (depending on coax type).
Analog security cameras can also be connected through simple network cable (UTP type Cat5/Cat6) which is cheaper than Coaxial cable.
UTP cables can be utilized by using Video Balun which converts CVBS signal into a “ Balanced Signal” form that is more suitable for UTP cables.
However most recent made security cameras has an internal video balun without the need for an external one, and it usually provides more than one connection options.
HD over Coax is a name for a set of technologies from multiple vendors, that allows sending HD video signals through long runs of coaxial cables, HD over Coax was invented to give old surveillance systems a chance to be updated from old CVBS based cameras to new HD cameras, without having to change old coaxial cables infrastructure to new cabling system such as UTP or Fiber.
Many HD over Coax technologies are competing to acquire the biggest market share, however four of these technologies are adopted most by security cameras manufactures:
1- High Definition Composite Video Interface (HDCVI): invented by the chinese Dahua company and currently licensed by other select manufacturers as well. The company claims that latest version (HDCVI4.0) can transfer 1080p video signal for a distance upto 400m, and 4k video signal for upto 300m through coaxial cables. Take care that these previous figures depend on the quality of the coaxial cable (ex. RG6, RG59).
2- High Definition Transport Video Interface (HDTVI): invented by the japanese-american Techpoint company, currently HDTVI4.0 is the latest version which techpoint claims it can transfer 1080p video for upto 500m depending on cable quality. Hikvision company - chinese camera manufacturing giant- is one of the biggest adopters for HDTVI technology.
3- Analog High Definition (AHD): invented by the korean NextChip company, it can support transferring 720p or 1080p quality for a distance upto 500m, Samsung lately adopted AHD in its cameras. however take care that there is multiple editions of this technology supporting, and each edition is supporting certain quality as follows:
a- AHD-L: also known as version AHD0.8 and it’s compatible with CVBS upto 960H.
b- AHD-M: also known as version AHD1.0 and it supports upto 720p and it’s back compatible with 960H.
c- AHD-H: which is AHD 2.0 and supports upto 1080p, and compatible with 720p and 960H.
so make sure before purchasing that your cameras are compatible with your DVR.
4- Serial digital interface (HD-SDI): which is an open standard for digital video transmission over Coax that were set as early as 1989, it can transfer upto 1080p video resolution but for much shorter distance -less than 100m- than can be reached by competitive technologies.
Although IP/Network surveillance cameras are the most expensive alternative, it's considered one of the fastest spreading technologies in surveillance cameras world as almost all new installations depend on it. Network cameras is connected through ethernet or WiFi, and a dedicated IP address -hence name- is reserved/pulled to/by each camera, usually you can access camera configuration Web Interface through the same IP with any standard internet browser. Also IP cameras can be grouped/networked through conventional network switches and routers. IP/Network cameras is known with its superior video quality that can reach - to the moment of writing- upto 8k quality, also it can work as a standalone device with the video being recorded on embedded memory card or even being sent directly to the an internet based cloud storage or display terminal, without even the need for NVR device.
IP cameras usually use video compression algorithms ( Mpeg4, Mjpeg, H.264 and H.265) to minimize bandwidth needed for video transmission so as to prevent network congestion and transmission latency which may raise problems in big installations if the network were not planned properly.
Off course video compression algorithms are usually lossy and may cause some degradation of fine video details, so an application specific evaluation should be held to balance between the minimum video quality required and the available bandwidth permitted by network type.
Modern IP cameras are usually compatible with the widely accepted ONVIF standard and have its logo, any ONVIF profileX (i.e X= G, Q, S, T, C, A) compliant cameras are guaranteed to work with any ONVIF compatible device that has the same profile. The biggest advantage of onvif, is that PTZ cameras with profile S can be controlled directly without the need for RS-485 network connection.(see section 2.3.3 PTZ cameras for more information).
Choosing the right housing for security cameras is one of an important factor in the success of the entire surveillance systems. Housing job is fixing camera in its position(i.e. wall, ceiling, poles etc) well with good coverage for site or room, also it determines whether installing external special application lenses is possible or not.
well-known housing types include dome, bullet, PTZ which will be covered later, BOX and the fisheye -some time named as 360’ or Panorama-. that later can be fixed in high ceilings, and provides a very wide field of view although its image may look deformed at edges.
Security Camera Housing is also responsible for the proper protection of camera lenses and electrical internal circuitry from tampering or environmental/weather conditions(rain, dust, snow, etc) according to installation location (i.e indoor or outdoor).
whether the security camera housing is suitable for indoor or outdoor installations, is determined by the its conformity to the “ingress protection” standard for outdoor conditions. for more information about ingress protection read this article.
These wonderful features enables merging camera power feed with video signal on one cable, which saves extra cabling costs and installation time.
PoE is found on IP cameras where power is fed to camera through UTP cables, and PoC is found on analog (traditional or HD) where power is fed through coaxial cable.
And it includes:
1st sensor type: because CCD sensors have better light sensitivity than CMOS sensors, and they can capture videos even in very dim light conditions.( see section 2.1.1 for details)
2nd Infrared leds: which provides an invisible lighting that can enhance night vision and extend camera range.
3rd ICR or IRCut: which is an acronym for (IR-Cut filter Removable). IR-Cut filters are used in daylight to avoid color distortion that may be caused by sensor infrared sensitivity, however in night or dim light time, sensor infrared sensitivity can be exploited to enhance image quality at low illumination conditions. Cameras with ICR feature can remove IR-cut filter mechanically to get better video.
PTZ is an acronym for (Pan, Tilt, Zoom). PTZ security cameras have motors that can move its lenses toward any specific point in camera surroundings(i.e pan and tilt), also motorized lenses gives zooming ability when needed.
PTZ cameras can be controlled by human operator or automatically through DVR/NVR if it has features like auto tracking or automatic/scripted PTZ moving feature.
In traditional types of PTZ cameras -still widely used- PTZ control signals are transferred to camera using a serial RS-485 connection between DVR and cameras, RS-485 can be used to make a “multidrop” network between devices. According to EIA-485 standard,RS-485 can connect upto 32 points(where point is a camera or DVR) in a bus topology network, RS-485 networks use a Master/Slave communication model, where the master (i.e DVR) is responsible of initiating/terminating all communication sessions on the bus, and talking to each slave(i.e camera) with its assigned address.
As the RS-485 is in the physical layer of OSI model, it doesn't contain any communication protocol specs, or any suggestions of how should DVR and camera exchange PTZ messages.
As there is no specific standard for PTZ protocol, Vendor specific protocols are usually used, however some of these protocols were open and gained some momentum between other vendors as Pelco-P, Pelco-D and Sony Visca.
Modern HD analog Security cameras use a group of technologies known as (UP The Coax) or simply UTC. UTC technologies allow sending PTZ signals in the same cable with the analog video signal without the need for a separate RS-485 cable.
To name some, UTC technologies include: Samsung CCVC protocol, Pelco-C, AHD-ACP and others.
IP Cameras also can combine PTZ SIGNALS -actually not only- with video digital stream through the ONVIF protocol, for more information about ONVIF and ONVIF Profiles see IP cameras section.
Wide Dynamic Range (WDR) and Back Light Compensation (BLC) features are used in case the scene in front of camera has very bright spots or very dark spots. high brightness spots may wash out or overwhelm adjacent image details as the camera may try to tune itself by iris or by reducing sensor sensitivity to cope with over illumination caused by bright spots.
difference between highest illumination spot and lowest illumination spot is called Dynamic Range, Security camera is described to have a “Wide Dynamic Range” if it can deal with a big illumination difference.
WDR feature works by taking two images -or more- for the same scene with a different exposure time that's appropriate for every high/low illumination spot, then by combining all images using a special digital image processor embedded in the camera we get an illumination/light balanced image.
BLC feature works by adjusting exposure time to get the ideal “mean” for light balance, of course WDR yields higher quality video because it's optimized for every single spot not for the whole image (see image below).
Electronic shutter turns on and off camera sensor periodically for a fraction of second to control the amount of light that camera sensor receives, it may also be called “exposure time”, a faster shutter (i.e small sensor exposure time) can “catch” better details of fast moving objects (i.e fast car number plate), and slow shutter speed gets fast objects look “blurry” or “ghost” like.
In general 1/50 second shutter period is suitable for most applications, it can be increased to 1/500 second for applications that have fast moving objects. Some cameras support upto 1/12000 second shutter speed !! (enough to catch helicopter blades in “still” position), however this last is practically applicable in most cases, as the more shutter speed the less light will reach camera sensor, so if you want to activate this feature, get sure that place monitored by the camera is well lighted.
We finished our first part of this guide, in which we talked about security cameras types and specifications. In the second part of this guide we'll talk about different types of surveillance video recorders and its features, and we will finish it with a section that talks about top security & surveillance systems manufacturers.