Before you build a video surveillance system, it is necessary to be clear about what you specifically want. There may be several parameters for selection of cameras such as the image quality, the installation method (external or internal), the illumination of the observed object, the angle of view (in other words the distance at which you can clearly see the object).

In video surveillance all cameras are roughly divided into two types - outdoor and indoor. From the title it is clear that some devices are intended exclusively for indoor use (apartment, office, garage, warehouse), while others are used in outdoor environment. A distinctive feature of the latter is the degree of protection IP-66, which means better protection against moisture (rain, snow) and dust, work at low temperatures (-30 ° C and below in the presence of the heating element), as well as the presence of a metal body, which significantly increases protection to the camera from mechanical damage by attackers.

Bullet cameras on the bracket are often used in outdoor conditions. Bracket allows you to set the camera at the desired angle. In addition, these models, unlike to the dome, have a visor that protects the lens from being hit by direct sunlight.

There is also an important factor for choosing a particular model in outdoor conditions. It is the range of IR illumination, which depends on the number and type of LEDs. If the distance to an observed object in a languid time of day is not very large (20-30 meters), use the camera on 24, 36, 42 of the LED. If you want to see the image at a distance of 40-50 meters and more, a model with a large number of standard LEDs (up to 72) or with LEDs III generation is required. As for the internal installation, it is possible to manage the cameras with illumination up to 10-15 meters.

Also, you need to choose the right lens focus. In the monofocal cameras (without the possibility of changing the angle of view) the default lens with a focal length of 2.8 or 3.6 mm. The lens can be changed to another with the focus 6, 8 or 12 mm, if necessary. The varifocal cameras (with adjustable angle) lens change is not necessary - the focal length is set manually and depending on model can reach 2,8-12 mm or 5-50 mm. What is it for? For example, if you installed a camera on the wall for an overall overview near warehouse territory, the focal length will be minimum. And over time, you changed your mind and decided to have a camera looking into the distance only, on the gate, for example. For this you just have to tighten up the lens and make a focal length maximum, then get enlarger and clear image of the object located far away.

And of course, while choosing a camera, you should understand how clear detailed images you want to monitor. If you need a general picture, which is enough to see a silhouette without details, video camera with 1Mp or 1,3Mp will be suitable. If it is necessary to clearly distinguish small details (the face of an attacker, items of clothing, the value of banknotes in bank or store), you can use the camera with a matrix on 2, 3 and 4 megapixels.