Video surveillance has ceased to be something unusual long time ago. In cities, we are observed from almost all sides by video cameras. Surveillance systems are installed not only in shops, offices, warehouses, parking lots, schools, kindergartens and hospitals, but also in apartments, private houses and in the surrounding areas. There are so many video surveillance systems out there these days, so choosing the right one for your needs can be quite difficult.
Surveillance system equipment
The main features of video surveillance are:
- Identification of various crimes;
- Monitoring employees in the office to prevent negative actions;
- Monitoring of shoppers in stores to prevent theft.
And for this, it is not enough to have only a camera – you need a full-fledged video surveillance complex, which includes:
- Surveillance cameras;
- Image transmitting equipment;
- Brackets and hermetically sealed casings;
- Recording equipment;
- Video recording processing devices;
- Motion sensors;
- And much more.
Criterias of choice
If you want to get a high-quality surveillance system, but you are not too well versed in them, we recommend choosing according to the following specific parameters:
- Recorder functionality. It should be equipped with the latest software to meet any need;
- Camera resolution. Not the most important, but still an essential parameter for selection;
- Possibility of remote viewing.
Types of surveillance systems
Various types of video surveillance systems are quite different from each other, so the choice of the right equipment must be approached carefully.
Analog systems that transmit a signal over a coaxial cable are no longer so relevant today, but still exist, so it is worth to pay attention to their description. Initially, the distance from the camera to the recorder for such systems was no more than 100 meters and the image resolution was only 720×756 pixels. Thanks to the improvement of analog system standards, it became possible to increase the resolution to 1 – 2 megapixels without raising the price of equipment. Several types of standards can be distinguished:
- AHD. The standard at which it is possible to transmit a signal at a distance of up to 500 m. Licenses for such communications are not required;
- HDCV. A standard with automatic signal correction features to help reduce distortion when using long communication lines;
- HDTVI. A standard that allows signal transmission over coaxial cable over a distance of half a kilometer, but communications can be of average quality;
- MHD. Hybrid option combining previous standards.
The most popular among professionals is the combined analog system, which allows you to unite the receipt of an analog signal and its recording. The recording device in such a bundle is a digital video recorder with a hard disk for data storage, an input for connecting a camera and an output for connecting to a screen. Comparing such a system with an all-analog one, it can be said that such a system is more practical due to higher recording quality and the absence of the need to change storage devices frequently. In addition, such a system can provide motion detection functionality, so recording can be performed only when motion occurs in the frame.
For the protection of critical facilities, hybrid systems are often used, which allow combining different technologies in one system. The recorder used in such a system allows you to connect both an analog and a network camera, as well as view video remotely, and not only on a monitor directly connected to it. But the price of such equipment is slightly higher than the previous option.
Nowadays, in addition to analog systems, there are completely network systems exists, based on IP video cameras with their own software on board and an IP address for communication. Recording in such systems is carried out on a video recorder made in the form of a standard server with installed video recording software.
Network video surveillance systems have their own advantages:
- Can work autonomously;
- Provides a higher quality image;
- Uses only one cord for power;
- It can connect an almost unlimited number of cameras, even several thousand;
- It can transmit sound;
- As a modern platform, it is easier to integrate.
Choosing a video surveillance system
Foremost, decide what kind of camera is needed: analog or digital. The analog camera transmits a signal in PAL or NTSC formats and connects directly to the monitor when recording requires purchasing additional equipment. But the image of such cameras of low resolution is only 720×576. Digital cameras, on the other hand, encode the signals received from the matrix and transmit them via computer networks to a recording device. The picture from these cameras is of the highest quality (for example, 1920×1080), so you can see not only the silhouette of a person, as on an analog one, but also small details.
You also need to decide where the video camera will be installed: inside or outside the building. For installation outside a building, outdoor models are best suited, having a special protective case that protects against temperature changes, precipitation, and vandalism. For installation inside, in rooms with high humidity, it is recommended to install cameras in hermetically sealed cases. Regardless of whether the camera will be installed (outside the building or inside), it is recommended to install them in hard-to-reach places to avoid damage to the equipment.
The third criterion for choosing a video camera is the viewing angle and focal length. If the task is to get a general overview of the protected area, you should purchase equipment with a short-focus wide-angle lens. If, on the contrary, it is necessary to observe only a certain small part of the site, or you need a clear recognition of faces, then you need a long-focus lens and a viewing angle of up to 45°. There are models in which the viewing angle, if necessary, can be manually changed. The focal length for manual adjustment can vary from 2.8 mm to 12 mm. These cameras are many times more expensive, but their prices are gradually declining.
The next thing to decide is what camera chromaticity is needed: monochrome or color. The advantage of monochrome devices is the low price and clarity of the picture in poor lighting, when the image from more expensive pure color camera in the same conditions will be with “noise”. Fortunately, color cameras are now being produced that automatically change the image from color to black and white at dusk.
Exposure sensitivity is also an important criterion for choosing a video camera. It determines the quality of the image in various lighting conditions of the observation area. Now almost all cameras are equipped with IR illumination, which will allow you to use the equipment at any time of the day. If the camera is going to be installed outdoors, it is recommended to opt for models with automatic iris switching that give a clear image at any time of the day.
WDR technology will help you get a uniform image regardless of the degree of illumination of objects. A device that supports wide dynamic range allows you to set the same level of illumination for the face and background in the image. This WDR system is used exclusively in high-grade video cameras, in budget you can only find its semblance.
When choosing a surveillance camera that will work around the clock, it's worth to pay attention to the presence of a day/night mode in it so that the camera can automatically switch to black and white mode at dusk. Powerful infrared illumination is also needed to help the camera display an image even in complete darkness. Regarding the task, the distance of infrared illumination can be from 5 to 50 meters. But do remember that some devices may have a mismatch between the viewing angle and the backlight angle, resulting in a blown spot on the image. Fortunately, there are cameras that automatically adjust the backlight power, which eliminates excessive illumination of the subject and the appearance of spots in the frame.
For small-scale objects, it is best to purchase a video surveillance system as a kit. This is more convenient because you do not have to manually select parameters for each individual element of the system. And it is more profitable because a ready-made equipment kit often has a lower price than the same equipment purchased separately. The kit contains everything that is necessary for its operation, besides, the compatibility of the equipment is guaranteed by the manufacturer. These kits are great for home or small office use. But for larger objects like warehouses and shops, it is better to purchase equipment separately, depending on the needs.
The installation of equipment and its transformation into a video surveillance system should be carried out by experienced specialists who can guarantee a long and high-quality operation of the system. However, now some kits are accompanied by a guide for self-installation and configuration, as well as the necessary tools for self-mounting equipment. Just remember that it is not recommended to mount the cameras on metal surfaces and near electrical wiring or other sources of electromagnetic radiation. Such external influences may cause noise and reduce image quality.