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Planning a video surveillance system — important aspects.
Planning a video surveillance system — important aspects
Usually you can be offered a color «super» camera, yes with radio transmission of a video signal, and even with IR illumination, but the main thing is — on outdated CMOS technology guaranteeing the presence of fixed and random noise and artifacts, with terrible image distortion when capturing a dynamic image, due again to the low sensitivity of the sensor.
A feature of CMOS TV cameras is considered to be a very low resolution — the most important characteristic of the CCD matrix — the sensitive element of the camera, onto which the view is projected and measured in TV lines.
Somewhere no more than 250-350 TV lines.
We recommend looking for cameras on CCD technology at least 380 lines or more for a color camera and from 420 TV lines for a black and white camera.
High-resolution video surveillance cameras — 470-500 TV lines for color or 570-600 TV lines for black and white are approximately 1.5 — 1.8 times more expensive.
Think about whether there is a need for this, because after digitizing and compressing the image on the DVR, the difference will be noticeable only slightly.
Very often the question is asked — how many meters to use a recognition camera.
The answer, as a rule, gives rise to new questions: everything depends on the optics and the place (distance) of installation.
Based on your task, the viewing angle of the lens is selected from the average distance to the intended object of shooting and what area in scope the surveillance camera with the lens will cover at such a distance.
This is natural, because the level of detail is determined by what part of the screen the object of observation will occupy.
With a high degree of certainty, in order to determine the silhouette of people, it is necessary for the object to cover one tenth of the screen of the video surveillance system.
To recognize a person you know, he “must occupy” 1/3 of the screen.
To recognize an unknown person, at least 2/3 of the person’s height must be “placed” in the full screen.
To determine the state registration number of a car, it must be placed in 1/4 of the screen.
The required focal length of the camera lens is determined based on these values using tables, a special calculator or a formula.
Perhaps this is the main secret of using video surveillance systems — it is impossible to ensure the recognition of details across the entire field of view of the camera.
It is necessary to think through the correct placement of video surveillance cameras, the strategy and tactics of their use.
Well, and of course the number of video surveillance cameras required to solve the task.
It is normal to prefer a color video surveillance camera to a black — white one, but it is not always an affordable luxury.
CCD matrices of color video cameras have significantly lower light sensitivity compared to black & white ones — the difference in time of day and in difficult lighting conditions of objects is very critical.
Ultimately, color video cameras in their pure form are rarely used in outdoor conditions.
If additional IR illumination is planned — it is necessary to take into account that it leads to defocusing of the image of color cameras and therefore the latter often have a filter that cuts off IR light.
Climatically, outdoor surveillance cameras are distinguished and for indoor installation.
Outdoor ones can be either heated, to avoid fogging of the protective glass, or without heating — sealed, do not freeze and do not fog up due to their own heat dissipation.
Indoor surveillance cameras are structurally manufactured as mini or in a standard case.
They can have a dustproof, moisture-proof, vandal-proof, explosion-proof casing. Their use is clear from the name.
It should be said that the type of execution does not speak about the quality of the surveillance camera itself, but only means the possibility of using more powerful optics, including those equipped with an ARD system for processing a wider light range.
Indoors, lighting is usually stable, expensive optics are not required, and therefore the capabilities of a miniature camera are sufficient. For installation of surveillance cameras outdoors in thermal housings, the use of optics with ARD is highly preferable, but not mandatory.
Automatic aperture control (ARD) of the lens allows for high-quality protection from side sunlight, reflected light from puddles, snow, headlights, spotlights and other powerful sources of illumination.
Lenses with ARD, as a rule, suggest better aperture ratio (F), are equipped with filters, which reduces the minimum sensitivity threshold in the dark and protects from illumination during the day.
In conclusion, I would like to recommend manufacturers of surveillance cameras that have proven themselves in the installation of video surveillance in Russian conditions.
These are South Korean cameras KT&C CNB Samsung and Sunkwang, Mintron YOKO, Merit Li-Lin, HI VISION cameras, Russian cameras MVK AVC Germikom, EVS and VSM, Japanese video cameras Panasonic, Sanyo, Computar and JVC, North American surveillance cameras Watec and Pelco.