Comparison Hikvision DS-2CD2732F-IS vs Hikvision DS-2CD2542FWD-IS

Operating range of the backlight (see "Design and capabilities") installed in the surveillance camera. This term usually means the maximum distance from the camera to the observed object, at which it is able to provide a relatively high-quality and legible image in the complete absence of other light sources. Of course, the actual backlight range may differ from the claimed one, and these differences are most often in the direction of increase (for example, due to the presence of the same additional light sources). However, if the possibility of shooting with backlight is important for you, you should focus on the claimed range.

Camera sensor resolution in megapixels (millions of pixels).

The higher the resolution of the matrix, the higher the video resolution can be (see below), the more detailed the image is capable of providing the camera. At the same time, note that as the number of megapixels increases (without changing the size of the matrix), the size of each individual pixel decreases, which increases the likelihood of noise and deterioration in the overall image quality. Therefore, high resolution in itself is not necessarily a sign of high quality — a lot depends on other things, for example, on the size of the matrix (see above).

As for specific values, in the most modest matrices it does not exceed 1.3 MP, which corresponds to the maximum HD resolution. 2 MP sensors allow for already Full HD resolution (usually 1920x1080 or 1600x1200), 3 MP, 4 MP, 5 MP and 6 MP are capable of better resolution, but still do not reach 4K, which is typical for 8 MP.

The maximum video resolution that the camera can capture.

The higher the resolution of the video, the more details you can see on it, the less details will be blurry. On the other hand, high resolution means large volumes of video materials, which, accordingly, requires capacious media for their storage and fast communication channels for broadcasting video in real time. Yes, and this indicator significantly affects the cost of the camera.

The lowest degree of illumination of the scene being shot, in which the camera is able to provide normal visibility. Usually, this item specifies the values for the daytime mode of operation (in the night mode, the minimum illumination in many models may be zero at all, because in such cases the IR illumination is turned on, see "Design and capabilities"). And if the camera is capable of shooting in colour, it usually means the lowest illumination necessary to obtain a colour image.

The lower this indicator, the better the camera works in low light, the brighter and more clearly visible image it is able to provide in such conditions. At the same time, note that in low light, night mode is often preferable, and in the presence of the aforementioned IR illumination, it is more likely to focus on the range of its operation (see above).

There are comparative tables that allow you to evaluate the degree of illumination indicated in the characteristics from a practical point of view: for example, an indicator of 0.2 lux corresponds to clear eyes on a full moon.

The signal-to-noise ratio that the surveillance camera corresponds to.

This indicator describes the ratio of the level of the useful signal (the actual image produced by the camera to an external device) to the level of extraneous noise that inevitably arises during the operation of electronic circuits. Such noise appears in the image as characteristic noise (“snow”). The higher the signal-to-noise ratio, the less interference on the screen, the clearer and better the image is, and the smaller the volume of recorded video files. It is believed that visible noise practically disappears at a ratio of at least 45 dB. However, among modern cameras there are also higher rates.

Type of camera lens by focal length. Here are the options:

— Permanent. Fixed focal length lenses have a fixed angle of view — in other words, they work at a constant zoom level and are not able to change it (the only option available for such cameras is electronic zoom). The advantages of CCTV cameras with a fixed focal length are simplicity, reliability, almost zero power consumption, small size and low cost. The main disadvantage is the inability to work with optical zoom (see below); and said electronic magnification is less advanced, since when approaching, the clarity of the “picture” decreases.

— Variable (varifocal cameras). Zoom lenses are more complex than "fixed" lenses, are larger, are considered somewhat less reliable, and are noticeably more expensive. However, this type of optics has an important advantage: it is the only one capable of providing optical zoom (see below), which allows you to “zoom in” the image without compromising its quality.

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.

Modern surveillance cameras can provide two types of magnification - optical and electronic. In the first case, the “approximation” of the image is carried out due to the operation of the lens; in the second, a separate area is selected on the matrix and the image from it is “stretched” across the entire frame, creating a magnification effect. Thus, optical zoom is more advanced: it allows you to use the entire sensor area even when zooming in.

Optical zoom is only available if the camera lens has a variable focal length (see “Focal”). And the degree of magnification will correspond to the ratio between the maximum and minimum focal length: for example, for a model with a range of 3 – 15 mm it will be 15/3 = 5x. Thus, we are not talking about how much the camera enlarges the “picture” relative to how it is visible to the naked eye, but about how much larger the image is at the maximum focal length than at the minimum.

The disadvantages of optical zoom systems are directly related to the disadvantages of variable focal length: the lenses are larger, more expensive and less reliable than with electronic ones. In addition, the capabilities of this operating format are limited: too high magnifications would require too bulky and expensive optical systems. Therefore, manufacturers often use a compromise option, supplementing optical magnification with electronic one: the first option is used at low magnifications, the secon...d is turned on when the capabilities of the optics are exhausted.