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

-LAN. The LAN (Ethernet) interface was originally intended for building wired computer networks. Cameras with this connector, usually, also work as network devices. The advantage of this option over the Wi-Fi described below can be called a higher actual bandwidth, over BNC — the ability to connect without additional equipment, directly to a standard network router used for a regular computer network. Of the shortcomings, one can only note the need to pull the wire, but this point is common to all wired connection options. For the rest of the features, LAN is the most convenient, thanks to which it has become widely used in modern security cameras.

— Wi-Fi. The 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 lack of wires, however, with an abundance of other wireless devices connected to the router, the channel bandwidth and image quality can noticeably deteriorate. Note that recently it is also possible to use this connection in the Direct mode — for direct connection of the camera with 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 commonly used for analogue video signal transmission. Refers to professional video interfaces, special equipment is required to work with such a camera. However, by themselves cameras with connectors of this type, usually, belong to the lower price range. This is due to limited connectivity via BNC — only a video signal can be transmitted through it, which limits the functionality of such cameras compared to models that work via LAN or Wi-Fi (see above).

— 3G / 4G. Internet connection via 3G / 4G mobile networks; usually, for this you need to install a SIM card from a mobile operator in the camera. The speed of such networks allows, among other things, to broadcast video in a fairly high resolution. So such a connection (of course, with coverage) is well suited not only as a fallback in case of interruptions to the Internet, but also as the main communication channel if there is no fixed Internet connection at all. A typical example of the second situation is the observation of a country house located "far from civilization", but in the zone of reliable mobile communication reception. Moreover, in both cases, you can contact the camera via the Internet from anywhere in the world.

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.