Answering this question needs a basic knowledge of the structure of a security camera
- type of system
- Camera housing(shape)
Choosing camera has some factor which involves in the matter of choosing the right one for right place.considering all these factors.
type of system:
There are many types of system available for cameras, it defines the type of connection and its options and limitations
- IP: based on a computer network, can work individually on a network and connects with network connection types (using LAN cable or WIFI if it’s wireless). It has a huge range of resolutions up to 12 Megapixels 4K and security and firewall and other security protocols. It considered as a standard that works on every computer network. it can connect to NVR (network video recorder) to save videos or any other storage devices on the network. POE (Power over Ethernet) option enables to run one LAN cable only as data and power connection together.
- High resolution up to 12 MP and 4k
- Secure connection
- Compatible with all networks
- Work individually
- POE available
- More expensive
- Up to 100 meters LAN cable range
- SDI: Serial Digital Interface (SDI) lets megapixel resolution pass through a coax cable (which use for analog low-resolution cameras). The resolution limited to 3 or 4 megapixels and the cable range is about 500 meters. POC (power over coax) is introduced to the market but haven’t tested on a long range. No certified security on the coax applicable as anyone can come in the middle of the cable and see the footage of the camera. Any factory has its own standards but the most common ones are TVI, AHD, CVI. It needs to connect a correct matched DVR (digital video recorder) to show the footage and record it. Ours called XHD as support all of them together.
- Resolution up to 3 or 4 megapixels
- Low security
- Compatible with its type of receiver
- Work in its system
- Reasonable price
- Up to 500 meters coax cable range
- CVBS: analog system, an old generation of CCTV known with analog terms of naming with TV-Lines (420. 540, 700TVL, etc.).it can directly connect to a CVBS receiver ( TV for example) and showing the usually, connect to DVR to save footage.
- Lowest resolution (half 1 megapixel or so)
- No security
- Work with any CVBS receiver (TV for example)
The image sensor employed by most digital cameras is a charge coupled device (CCD). Some cameras use complementary metal oxide semiconductor (CMOS) technology instead. Both CCD and CMOS image sensors convert light into electrons.
The size of CCD is a vital factor to concern affecting the quality of the image as it gets larger the quality becomes higher.
The most common sizes in CCTV systems are 1/3 inch and 1/2.8 inch.
The lens enables light to focus on the CCD in a right distance to produce clear images. Lens numeric and its calculation is complicated especially when it comes to focusing calculation. however, there are some standards to make it easy to use called focal. The distance of target to the camera can be evaluated by choosing the right lens.
When the focal number of millimeter gets higher the image becomes more zoom.
2.8mm can see 86 degree (wider) while 12mm can just see 32degree ( narrower )
but when it zooms you get to more detailed image obviously.
There are some different lenses type.
Fix focal: with fix diameter and focus point (e.g. 3.6mm or 16mm)
Variable focal: adjustable on different diameter and focus point (e.g. 2.8-12 mm)
Also, there are some lenses that can control the diaphragm (named IRIS) to control the amount of light enters to the camera. This can be automatic or manual.
The body of camera define its mechanical abilities and most companies name their products by the shape of the camera.
- Bullet: Usually to use for outdoor. Bigger size to be seen easier. Usually water and dust proof or resistance showing by IP Number (International Protection). Mainly equipped with static color and stronger night-vision. Also, bigger housing enables it to have more utility such as zoom lenses or heating or cooling.
- Dome: round shape of the camera makes this type more convenient to use indoor and under roofs. Also, it might be more vandal resistance due to its mounting and shape. Equipped with night vision and some models zoom lens.
- PTZ: Also known as Speed Dome or Moving camera (dome) is a round shape camera. this is the most equipped camera body, enables it to move in any direction and zoom (wide to narrow look) and focus on objects with its 360-degree rotation. As an option, it may zoom on and follows a moving object for a specific time (Auto track) or patrol an area. Mostly has night-vison function and has a heater and cooler and protection against water and dust.
WDR: If you have a source of light behind your target, it is hard to have a clear image with details as it shows dark on video. Wide dynamic range (WDR) automatically adjusts bright and dark to avoids overexposure in this situation.
Compression: As the image, footage needs the high capacity to store, compressions helping to reduce the bandwidth of sending data in order to save more space to record for longer. However, it may drop the quality. There are many of compression method, and the usual one for CCTV is H.264 and the newest one is H.265 which can compress more with much less quality drop.
FRAME RATE: Number of frames that can be seen with the human eye is 30 frames per second. How many more frame you can see with your camera in a second, it becomes smoother in the eye.