Comparison Hikvision DS-2CD2021G1-IW vs Hikvision DS-2CD2021G1-I 2.8 mm

— LAN. The LAN (Ethernet) interface was originally designed to build wired computer networks. Cameras with such a connector, as a rule, also work as network devices. The advantage of this option over the Wi-Fi described below is a higher actual throughput, over BNC — the ability to connect without additional equipment, directly to a standard network router used for a regular computer network. Of the disadvantages, one can note only the need to pull a wire, but this point is common to all wired connection options. In terms of other features, LAN is the most convenient, due to which it has become widespread in modern surveillance cameras.

— Wi-Fi. Wi-Fi connection was originally a wireless analogue of the LAN described above and was used to connect to computer networks. When working in such networks, this connection is similar to LAN in the sense that it allows the camera to work through a regular router (of course, supporting Wi-Fi). At the same time, Wi-Fi is more convenient due to the absence of wires, but with an abundance of other wireless devices connected to the router, the channel throughput and image quality can significantly deteriorate. Note that recently it has also been possible to use this connection in Direct mode - for direct connection of the camera to another device, for example, connecting the camera to a smartphone (see "Design and capabilities -...P2P"). However, this option is less common.

— BNC. Abbreviation for Bayonet Neill Concelman. A bayonet-type connector, usually used to transmit an analog video signal. Refers to professional video interfaces; special equipment is required to work with such a camera. However, cameras with this type of connector are usually in the lower price range. This is due to the limited connectivity options via BNC — it can only transmit a video signal, which limits the functionality of such cameras compared to models that work via LAN or Wi-Fi (see above).

— Aviation port. It is a round multi-pin connector designed for reliable connection of cameras. Such ports provide a stable connection even in conditions of vibration and high humidity, due to which it is used in car video surveillance systems. Power, video signal and control (for example, for PTZ cameras) can be transmitted through one aviation port, which simplifies installation and reduces the number of required cables.

— 3G / 4G. Connecting to the Internet via 3G / 4G mobile networks; as a rule, this requires installing a SIM card from a mobile operator in the camera. The speed of such networks allows, among other things, to broadcast video in fairly high resolution. So such a connection (of course, if there is coverage) is well suited not only as a backup option in case of Internet outages, but also as the main communication channel if there is no fixed Internet connection at all. A typical example of the second situation is monitoring a country house located “far from civilization”, but in an area with reliable mobile phone reception. In both cases, you can contact the camera via the Internet from anywhere on the planet.

Focal length of the camera lens.

The focal length is such a distance from the lens to the matrix, at which a clear image is obtained on the matrix (when the lens is focused to infinity). The viewing angles of the lens primarily depend on this indicator (see below): the smaller it is, the wider the viewing angles and the smaller the objects in the frame (and vice versa). At the same time, it should be noted that the actual viewing angle is determined not only by the focal length, but also by the size of the matrix (see above). In fact, this means that with different sizes of matrices, lenses with the same focal length will have different working angles. Therefore, only cameras with the same matrix size can be compared with each other according to this indicator. Among CCTV cameras, lenses with a focal length of 2.8 mm, 3.6 mm, 4 mm and 6 mm are considered popular.

In models with a variable focal length (see above), in this case, the range from the minimum to the maximum distance is indicated. Also, using these data, you can derive the optical magnification factor of such a lens: for this, the maximum value must be divided by the maximum (for more details, see below).

Horizontal viewing angle of the surveillance camera. For models with a variable value, the maximum value is indicated, since it is the width of the image that is important, and when zooming in, the zoom factor is more important than the angle. This paragraph also indicates the general angle of view for models with a circular field of view – in particular, cameras with a fisheye lens (see above)

The wider the viewing angle, the more space the camera captures and at the same time, the smaller the images of individual objects in the frame are obtained. Therefore, when choosing by this parameter, it is worth deciding what is more important – the ability to view a large scene or the visibility of small details in a relatively narrow field of view. Also note that with a wide field of view (100° or more), characteristic distortions can be observed at the edges of the frame, and the wider the angle, the more pronounced they are. This phenomenon can be eliminated by panoramic shooting (see "Design and features"), but this feature, in turn, complicates and increases the cost of the camera.

Vertical viewing angle of the surveillance camera. In models with a variable value, the maximum is indicated, and the angle when zooming is not so important.

The wider the viewing angle, the more space the camera captures and at the same time, the smaller the images of individual objects in the frame are obtained. Therefore, when choosing by this parameter, it is worth deciding what is more important – the ability to view a large scene or the visibility of small details in a relatively narrow field of view.

The video compression format used by the camera.

Compression is used to reduce the file sizes of captured video; different technologies can be used for this — the so-called codecs, their list is given in this paragraph. From a practical point of view, compatibility with external recording and playback devices primarily depends on the supported codecs. If you plan to use a computer as a recorder / player, you can ignore this list: modern PCs and laptops usually support a very extensive list of formats, and in extreme cases, the missing codecs can be installed separately. But if we are talking about specialized registrars, individual players (like home media centers), etc. — codec compatibility should be clarified further. So, if the advanced modern H.265 standard is very widely supported nowadays, then the more specific H.265+, originally created for surveillance systems, is much less common even in specialized equipment.

The main material used in the construction of the camera body.

— Plastic. Inexpensive and at the same time quite practical material. Plastic is light, quite strong (not as strong as metal, but still quite sufficient for most cases), chemically inert (and therefore not susceptible to corrosion and insensitive to moisture), and also has a relatively low thermal conductivity (which provides additional protection for extreme temperature fluctuations). Due to all this, this material is very popular in indoor chambers (see "Usage"). At the same time, it is somewhat less suitable for outdoor work.

— Metal. The main advantage of metal, in comparison with plastic, in the case of surveillance cameras is high strength and reliability. This allows you to use it even for street models that work in difficult conditions and must have a certain anti-vandal resistance (at least not immediately “give up” when trying to break or break). At the same time, such material is much more expensive, and therefore less common.