Security cameras are the “eyes” of any video security system and they must be suitable for the environment in which they are in. The desired image you wish to capture will narrow the available choices. For example: Do you need to identify the type of car during playback? The make and model of the car? The license plate? In total darkness? 20 degrees below freezing? All of the the above?
There are two basic types of security cameras: analog and digital, also referred to as IP cameras. Analog cameras are more affordable and send an analog video stream to a video recorder where it is digitized and stored. IP cameras encode (digitize) the image at the camera and optionally send a high resolution digital image to a network video recorder (NVR) or other file system which stores the images eliminating the need for processing power at the collection point. Analog cameras are limited to resolutions of approximately 550 lines of resolution (roughly 0.3 megapixels or 704×480) where as IP cameras are emerging allowing for extremely detailed images with multi megapixel resolution.
Security cameras come in a variety of forms such as bullet, dome, discreet (“spy cameras”) and traditional box cameras – most forms are offered in indoor and outdoor formats with the exception of box cameras which need to be installed inside housings that are commonly seen at gas stations. Other forms include covert ‘lipstick’ cameras, radio clock cameras, smoke detector cameras and sprinkler system cameras. Security cameras are usually permanently mounted and the location may influence the camera choice based on aesthetics. For example, homeowners may wish to use discreet cameras that blend in with the surroundings where as businesses may want cameras visible to act as a deterrent. Surveillance cameras should be mounted to cover either assets themselves (cars, cash registers, machinery, people…) and/or ‘chokepoints’ such as hallways, doorways, driveways or pathways. Narrow paths are ideal because there is a high degree of certainty that objects will pass through the view of the camera.
For environments where it is necessary to have more control over the camera, PTZ cameras exist allowing the operator to pan, tilt and zoom the camera as required. PTZ cameras are much more expensive than their fixed counterparts because of the extra electronics and motors required to move the lens around. Additional wiring is required to control analog cameras and attention must be paid to ensure that the camera is compatible with the DVR, if that is what will be used to control the camera movements. PTZ cameras have their place and usually require a full time operator to make them effective. Newer technologies such as “auto tracking” PTZ cameras allow the camera to detect and follow motion, reducing the need for human intervention. There are also surveillance cameras with automatic pan which simply move back and forth along a predetermined path. This can be a cost effective solution to monitor large sites. Some IP cameras offer ‘virtual’ PTZ views which are unique views from the same high resolution images.
There are several important features about cameras, regardless if they are analog or digital:
- Resolution – the amount of detail that a camera can capture. Resolution is *the* most important factor in choosing a camera. Analog cameras have a maximum resolution of ~0.4 megapixels (read why) and require a focused field of view to be able to capture an image with adequate detail. IP cameras will provide specifications just like a point-and-shoot camera – in megapixels instead of horizontal lines of resolution and usually start at around 0.3 megapixels and go to 10MP or higher. IP cameras usually record progressive scan video or whole frame video versus analog’s interlaced implementation which can yield poor results when recording objects in motion.
- Minimum Illumination – the lowest possible light in which a camera can capture a useful image, usually measured in Lux. Lux is commonly defined as “lumen per square meter”. A full moon provides approximately 0.1 Lux. Street lighting provides approximately 1 to 10 Lux. The camera you choose needs to be able to handle all light variations that your environment will present. Black and white cameras are the only option for low light situations. Learn about night vision cameras which use infrared emitters to allow cameras to capture detailed images with little or no light (0 Lux).
- Environment – this is a critical specification if you wish to install a security camera outdoors, especially in colder or tropical environments. Indoor cameras are typically less expensive than outdoor cameras. Every camera has a minimum and maximum operating temperature and some outdoor security cameras use heaters and blowers to achieve wider ranges. The International Protection Rating helps by indicating if a camera can be placed in wet or dusty environment. Vandal resistant cameras are also common, some able to resist a strike from a baseball bat.
- Focal length – commonly referred to as “lens” in product specifications. This measurement will determine what the camera’s view will be based on how far it is from the object you are monitoring. Varifocal lenses are popular as they allow the installer or end user to fine tune the field of view onsite to capture the best picture possible.
- Mounting – thought must be given to where the camera will ultimately be placed as it will dictate the type of mount (ceiling, wall, post) that can be used and whether or not the lens can easily be adjusted.
- Cost – as with most things in life, you get what you pay for. You could have the best DVR but will get poor results if a quality camera is not used.
- Image sensor – attributes of the electronics that capture the image from the lens. In addition to size (1/4″, 1/3″ and 1/2″ are most common), the quality and type of the sensor are also considerations. Higher quality sensors will result in better detail including environments where there can be contrasting levels of light such such as a store front window. Cheap lenses, sometimes made of plastic, will yield poor results.
- Connectivity – the video signal from analog cameras are usually carried using coaxial cable such as RG59 though CAT5 cable can be used with the use of baluns. Analog cameras also require 12V or 24V power. Being purely digital, IP cameras can use common CAT5 or CAT6 cable are are usually powered by PoE switches or PoE injectors – one cable does it all.
Budget can often dictate whether analog or digital (IP) based video security systems are used. Both can capture a useful image when properly implemented.