22 May 2009 Comments Off on How to Choose Good Quality Security Cameras

How to Choose Good Quality Security Cameras

The best security cameras consist of two basic, but very crucial elements – the quality of the image sensor and the quality of the parts and engineering of the camera components themselves. Listed in the specifications of each surveillance camera, you will find out who makes the “guts” of the camera. In other words, what name brand chipset is at the heart of this camera? There are numerous brands out there, but the top two are Sony and Panasonic. Both of these brands will give you an excellent picture and the longest life. Both Sony and Panasonic offer several levels of chipsets, so always look for these minimum performance parameters, no matter what type or style of camera used, or who’s name is on the outside:

  • Type: Grade “A” CCD (Charge Coupled Device) Imaging Chipset, or DPS Chipset CMOS

  • Format: 1/3” or ¼” focal length (1/3” gathers more light and has a wider view, but ¼” is fine for high resolution models in well lit areas)

  • Color or Day/Night operation: (Day/Night versions turn from color to Black & White under low light conditions)

  • TV Lines of Resolution: 380 to 400 lines for medium resolution cameras, and 480 to 560 lines for high-resolution

  • Signal to noise ratio (S/N): at least 48db or higher (50db+ is visibly better)

  • Voltage: 12V DC is fine for smaller cameras, while 24V AC is usually better, and is required for any camera with heaters.

Lenses are the most important part –

The human eye is an incredibly adaptable device that can focus on distant objects and immediately re-focus on something close by. It can look into the distance or at a wide angle nearby. It also has a long ‘depth of field’, therefore scenes over a long distance can be in focus at the same time.

By contrast the basic lens of a CCTV camera is an exceptionally crude device. It can only be focused on a single plane, everything before and after this becomes progressively out of focus. This single focus point must be predetermined and that is usually not a guarantee that an occurrence that you want to see will happen in that area. Therefore, the selection of the most appropriate lens for each camera must frequently be a compromise between what you expect to see and the practical use of the system. It’s not feasible to see the whole wash bay and be able to read all the license tags with one lens. The solution may be to add more cameras or to compromise with a lens strength that is somewhere in between.

One of the best lens types to work with when you install your system, is the “Varifocal”, or manually adjustable zoom lens. This type of lens gives you a small amount of adjustability to “fine tune” each scene, whereas a “fixed lens” camera is pre-set to a particular view. As adaptable as the Varifocal lenses are, I’m always tempted to use them everywhere. However, depending on which area of your home or business you want to cover, they’re not always the best choice when considering both price and effectiveness.

The following is a list of the most common types of lenses used and where I have found they work best:

Fixed Lenses View is fixed and cannot be altered: Least costly and usually comes standard with a 3.6mm lens (see sidebar for lens views) or can also be ordered with other options as well. A simple camera to use. Arrives pre-set and pre-focused so all you have to do is hang it, plug it in, point it and you’re done. Used for short distance shots and general wide-angle views.

Varifocal Lenses Small amount of adjustability is provided to get the correct width and distance: Available for about $20 more on most cameras. The amount of adjustability varies with each lens, but try to get a security camera with a 3.5mm to 8mm range for Bays, a 2.8mm to 12mm range for wide-angle views of outlying areas, and a Telephoto range of 5mm to 50mm or more when using the camera to capture license tags.

Zoom Lenses Usually electrically operated and most commonly a part of a Pan/Tilt/Zoom type security camera: Pan/Tilt/Zoom cameras, or PTZ’s, are nifty gadgets that can be used to do the job of several cameras, and have many tricks up their sleeve that can be really helpful. These types of surveillance cameras can not only be remotely controlled over the Internet from your PC, but can also be programmed to perform tours and go to preset positions automatically or upon an event. For example: you can have the camera panning, then zoom in to capture the license tag, then on to the next area you want to record. You can interrupt the camera to move it around, then make it go back to it’s primary job. Some of the nicer models even have several inputs so that you can attach some type of external sensor to trigger the camera to swing around and capture a license tag on a passing car, or to zoom in on a certain area when there is activity.

The PTZ cameras are certainly a nice tool to have and also make a nifty toy to play with on slow evenings at home, but they do have a few drawbacks that you need to be aware of. Price is the first consideration. Good quality outdoor rated PTZ’s and accompanying accessories can run close to $1300 each. In some cases you may be better off with stationary cameras that constantly monitor a scene rather than a moving camera that may miss something that happens when it is looking elsewhere. Also factor in the fact that PTZ security cameras are a mechanical apparatus that will eventually wear out and will need more maintenance than simpler cameras, especially if you have them moving constantly.

Written by: Allen Spears, Chief Engineer, Rugged CCTV, © Copyright

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