Bullet cameras are shaped like cylinders, and get their name from the fact that they resemble bullet cartridges. Bullet cameras come with weatherproof housings and are often used as part of outdoor CCTV surveillance systems.
Most bullet cameras have a fixed 4mm lens. A 4mm camera lens lets you to see facial features out to approximately 35 feet. A 4mm lens allows provides about a 70° viewing angle, which is the widest angle you can have without suffering picture distortion.
Day-Night Security Cameras
Day-night cameras, also called low-level cameras, employ a very sensitive digital chip that can capture scenes in very low-level lighting conditions. During the day, the camera takes images in color while at night it automatically switches to black-and-white mode when the light level drops a certain amount. These cameras do need some light in order to take images, even if it is the light of the moon or stars.
Some people confuse day-night cameras with infrared cameras but they are not the same. The latter use infrared illumination for their operation to see without any light at all.
Dome cameras gets their name from the plastic dome housing that the camera is enclosed in. They are most often seen in retail businesses and office buildings. Often the dome is dark tinted making it hard to see where the camera is pointing.
Dome security cameras are very tough and some models come with high-impact polycarbonate housings that will withstand heavy blows, making them ideal for locations with high-potential vandalism.
Hidden cameras, also called spy cameras or covert cameras, are designed to be very small and either hidden from view, concealed in everyday objects, or disguised.
Most hidden camera are pinhole cameras, which feature a small lens that can see through a tiny pinhole opening, such as behind a wall.
Infrared cameras, also called night-vision cameras, use an infrared light source near the camera lens to illuminate the area with infrared light, which people cannot see. This allows the infrared camera to see in conditions with no light at all, such as inside dark offices at night. With just a slight amount of normal light, an infrared camera can take a picture that looks as good as that in daytime. Most infrared cameras take pictures in black-and-white.
One problem that infrared security cameras can experience when placed in outdoor housings is light reflection from the front glass cover of the housing. By placing the camera lens flush with the housing, this problem can be minimized.
Some people confuse infrared cameras with day-night cameras but they are not the same. The latter do not use infrared illumination for their operation.
Outdoor Security Cameras
Outdoor security cameras are housed in special weatherproof enclosures or housings that protect them from tough weather and temperature conditions such as rain, snow, wind and the sun. Some enclosures utilize electric strip heaters and fans. The strip heaters help keep the humidity down for the electronics, prevent condensation from forming on the housing cover and camera lens, and provide heat in cold environments.
Other security cameras meant to be placed in high-crime or high-vandalism areas feature tough "armored" enclosures that can withstand heavy blows.
PTZ security cameras feature a motorized mount that allows the camera to be moved remotely up-down and side-by-side. In addition, the camera has a motorized zoom lens that can be moved in or out.
Digital Video Recorders (DVR)&Network Video Recorder(NVR)
Digital video recorders (DVRs & NVRs) have replaced older analog CCTV system equipment such as multiplexers, quads, time-lapse VCRs and videotapes over the last few years. A digital video recorder allows live camera images or previously-recorded video images to be viewed on your computer over a computer network or over the Internet. All digital video recorder equipment can be setup to record only images where motion is detected on the camera field of view. This saves you from having to play back hours of video footage that doesn't change. Digital video recorders for video surveillance are available with 4, 6, 8, 10 and 16 video camera inputs.
A DVR can be connected to a CD or DVD burner, computer hard drive, or other mass storage device. PC-based DVRs are also available - these consist of a PCI card that is installed in the computer along with software. This kind of DVR with CD burner can be set to email you or even call you on your cell phone if a motion is detected one of the cameras.
Other features of a digital video recorder surveillance system include motion sensing, selectable alarm triggers and pan-tilt-zoom camera support. As part of your CCTV package, all video, audio, alarm and control signals are sent over the Internet.