A: The iris controls how much light is let into the camera lens. In the old days, cameras came with no iris control. If you needed to control the light levels you would have to purchase a special lens. Nowadays, most cameras come with automatic shutters which perform the same function as the iris - controlling how much light is let into the camera. Unless you have an application with extreme light levels (like at a beach) you probably won't need a special lens with iris control.

A: A Pan Tilt Zoom camera (PTZ) allows you to pan (back and forth), tilt (up and down), and zoom (focus in and out) your camera remotely. The PTZ is controlled using a remote PTZ controller or you can control it through most DVRs (look for PTZ support). The disadvantages of a PTZ camera is that they are very expensive (usually around $1000 without the controller). And all the moving parts make it susceptible to wear and breakdown. There are some new digital versions of PTZ cameras just coming on the market that have no mechanical parts. These PTZs are very promising but are still a little too expensive to be practical for most uses. PTZ cameras require a data cable to be run to the camera in addition to the video and power cables. Unless you have a person who is watching the scene and adjusting the field of view of the camera based on what's going on its not as useful. Most times you are better off buying more of the non-PTZ cameras to continuously cover the area rather than a PTZ.

A: DVR Cards enable the user to convert their computer into a Digital Video Recorder. The DVR Card(s) is typically installed in an available PCI slot of a computer. DVR cards are bundled with video surveillance software which allows the user to record and display multiple cameras simultaneously from the camera site or a remote location.

A: Wired cameras have a video cable that runs from the camera to your recording or viewing device such as a DVR, VCR or monitor. Wireless cameras have a built-in transmitter that sends the video signal to a receiver. The receiver connects to your recording or viewing device.

A: The amount of time a DVR will record for is based on the size of the DVRs hard drive, the number of cameras recording and the number of frames per second it is recording at. One camera recording in Real Time uses 1 GB per day. So a 16 camera system will use 16 GB in one day.

A: A fixed focal length lens cannot zoom. The focus is fixed. A fixed focal length lens usually allows more light to pass through the lens at a given focal length than a varifocal, or zoom lens. This can be important in low light situations.

A: A varifocal lens is one where the focal length of the lens can be varied. This is a fancy way of saying it is a zoom lens. Most varifocal lenses have, and in almost all circumstances should have, an auto iris feature.

A: CCD is used in professional cameras because of it's high resolution quality and it's ability to record in low-light situations. CCD is basically a small silicon chip that receives light and turns it into voltage variations which makes up an image. It's usually measured in inches with 1/3" CCD being the standard. They are higher priced but are great for cameras that may require vision in near darkness.

A: Standard wireless hidden cameras can transmit up to 1000 feet and high-powered wireless hidden cameras can transmit up to 2000 feet.

A: A small board camera is built into an everyday item. The camera can be wired which means it is connected to the DVR or VCR using a cable. The camera can also be wireless, in this case the camera transmits a signal to a receiver that is connected to the DVR or VCR.