A Manager's Checklist for Cameras

(09/02/2010)

There are a number of questions that need answering when considering current and future cameras. Some will be answered thanks to the expert help of a systems integrator, A&E consultant or product manufacturer.

An Infinova white paper establishes a manager's checklist for cameras.

Among the Basics:

• What do you want the cameras to see and what is the distance?
• What types of lenses are needed? Wide-angle, normal, telephoto? Can varifocal lenses be used?
• What resolution is needed for each camera?
• Are megapixel, high-resolution or high definition cameras needed? How about thermal?
• Can the video management system accommodate the features of the cameras?
• Are licenses required for the digital cameras?
• How many images per second are needed for each camera?
• What is the total number of cameras required? Fixed or pan-tilt-zoom (PTZ)?
• What types of cameras are needed: dome/mindome cameras? Bullet cameras? Enclosures? PTZs? Wall or ceiling mount?
• If PTZ cameras are needed, are operators available, or will the PTZs be set on an automated panning pattern? Or will the PTZs be digital so they can be zoomed or moved after a recording is made?
• Are cameras in a special environment requiring enclosures, such as explosion-proof housings?
• What type of ceiling and walls are available? (Dropped ceiling, hard ceiling and walls, drywall?)

Among the Areas to Cover:

• Are cameras needed outside?
• What areas do you want to cover outside? Entrances, parking lots, open spaces, fences?
• Do license plate numbers have to be read?
• Is there any illumination at night? Are infrared illuminators needed? Day/night cameras? Thermal cameras?
• Are dome cameras appropriate or enclosures for cameras?
• Are heaters or blowers needed due to weather conditions?
• What type of wire is needed from the cameras: coax, twisted pair, Cat 5e, fiber-optic? Is it already installed?
• Can power over Ethernet (PoE) be used?
• Where are or will the power supplies located?

Housings and Enclosures

Dome cameras are a good choice for video surveillance systems to address either of two basic needs. When the installation requires the added power and flexibility of a pan/tilt/zoom camera, dome housing is necessary to enable the camera to have an unobstructed view no matter where it is looking. And some end-users see value in dome housing even when using a fixed camera for wall-mount or ceiling-mount applications because the dome can provide a more pleasing appearance. Of course, use of a dome, often smoked, means the bad guy doesn’t know if the camera is pointing at him or not.

Whether PTZ or fixed domed cameras are part of a legacy installation or when buying new gear, security executives need to consider the environment in which the camera will work. Some cameras have vandal-resistant and ruggedized domes, which can be important when a camera is mounted in an area that could be reached with a baseball bat or weapon. Other cameras may require a separate housing for vandal protection. Putting autotracking within a camera enclosure can speed reaction time as a PTZ dome camera follows a subject.

Special housings also may be needed if a camera will be installed outside. In certain climates, there is need for a heater and, for certain areas, need of a hidden blower. Sunshields also can play an essential role for some outdoor applications. Depending on an end-user’s type of business or industry, housings that protect from water damage or dust are available as are housings with a pressurized seal.

What about the Lens?

The lens is the second most important choice in a security video system after the camera. One of the reasons lenses sometimes are taken for granted is that many video cameras, particularly popular dome cameras, come with a lens already built in.

To determine the right lens, the manager needs to consider how far away and how wide an angle each camera needs to see. So why consideration of a lens when some cameras come with one? Lowend solutions often include the camera and lens. But in crucial applications, more appropriate solutions include an integrator’s selection of a lens for each camera based on the scene and lighting of the view.

There also is the issue of megapixel lenses for HD or megapixel cameras. Without the correct lens, a megapixel camera may not produce the high resolution images to match the capability of the camera’s sensor. The lens bottom line: When selecting a megapixel lens make sure the megapixel resolution power extends across the lens’s entire field of view, not just in the center. Some lenses, often lower priced, produce megapixel resolution only in the center of the lens; at the periphery, the resolution can be far less.

Some key questions include:
• What is the lighting in the installation area (indoor and outdoor)?
• Do you just want to see activity in an area or to specifically identify someone or something?
• How far away will the person/object to be identified be?

There are differences and situation advantages among fixed, varifocal and zoom lenses. Fixed focal lenses have a single millimeter number and can be slightly less expensive than varifocal lenses, which have a range of settings, such as 2.6 – 6 mm (wide angle), 3.5 – 8 mm (medium angle), and 5 – 50 mm (long distance). Even though they cost a little more, varifocal lenses are flexible in most situation except where objects are a long distance away. Motorized zoom and telephoto lenses work with fixed cameras and, of course, PTZs. They have longer reach to hone in on a specific of the total image and often are used for specialty scenes and applications. End-users often have standardized on varifocal lenses for their fixed cameras.

Aspherical, Standard Lens; Manual, Auto Iris

Aspherical lenses – high end but not necessarily high priced -- have highly polished, computer-designed convex surfaces that let in more light than standard lenses and hold image focus better from center to edge. The technology is smaller in size, can correct for color aberration and lowers the lens f-stop number for increased light transmission. The iris in a lens is like the iris in the human eye; it opens and closes in response to light. Irises in manual iris lenses are set to one fixed f-stop opening and are best where lighting is relatively constant. Auto iris lenses have an electronically controlled iris that opens and closes as the light changes to maintain a constant video level image.

Focal Length – Camera and Lens Together

Focal length, measured in millimeters, is the distance from the center of a lens to the sensor. The longer the focal length, the narrower is the angle of view; the shorter the focal length, the wider the angle of view. To calculate the field of view or lens focal length of a security video camera, you must know some parameters of the installation. Among those parameters:
• Distance from Camera - Maximum distance from camera to the target.
• Camera Installation Height.
• Field of View – Height.
• Field of View: Width.
• Camera Sensor Format.

Read part 2 of this white paper

Related topics:  CCTV cameras and domes   IP monitoring   Knowledgebase   White papers 

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