Comparison Tecsar AHDW-20F3M vs interVision 3G-SDI-3100W

The number of backlight LEDs (see "Design and capabilities") provided in the camera design.

Theoretically, more LEDs provide more power and, accordingly, range (see below) and efficiency of IR illumination or LED illumination. However, in fact, such light sources can vary markedly in performance; in addition, a lot also depends on the features of the camera itself. Therefore, in fact, this indicator is a reference, and when choosing, it makes sense to pay attention to parameters that are closer to practice — in particular, the same backlight range (see below).

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.

Model of the matrix installed in the surveillance camera. Knowing the exact name of the model, you can find detailed information about its operation — from detailed specifications to real user reviews — and assess how this option meets your requirements.

The size of the matrix installed in the surveillance camera (diagonally).

In general, larger sensors (with the same resolution and sensor type) are considered more advanced: they get more light, which has a positive effect on image quality (especially in low light). On the other hand, increasing the size affects the cost of the entire device; and in some cases (for example, if the camera is not planned to be used in twilight and darkness), a relatively small sensor may be quite suitable.

As for specific dimensions, the most modest cameras in terms of this indicator have matrices of 1/4 "or less. Models with sensors of 1/3.8" - 1/3" and 1/2.9" - 1/2" are very popular, these values can be called average. And in advanced devices, diagonals and more than 1/2 "(up to 1/1.7") are found.

The maximum frame rate in the video captured by the camera.

The higher the frame rate, the clearer the image, the less noticeable blurring when moving in the frame (especially fast). On the other hand, this indicator affects the amount of information recorded during shooting, as well as the cost of the camera itself. Therefore, it makes sense to specifically look for a video surveillance camera with high-speed shooting(45 fps and higher) only if a clear recording of fast moving objects is important to you.

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.

Aperture of the lens installed in the camera.

Aperture characterizes the degree of attenuation of the light flux when passing from the front lens of the lens to the matrix. It is denoted as the ratio of the diameter of the active aperture of the lens to the focal length, while the size of the active aperture is designated as f and is taken as a unit — for example, f / 1.4 or f / 2.0. Moreover, the smaller the number in the designation, the higher the aperture (in our example, the second lens will be darker than the first). And for lenses with a variable focal length (see "Focal"), the actual aperture, usually, changes with a change in focal length; for such models, either the range of aperture values, or its maximum value, can be indicated.

By itself, this parameter characterizes, first of all, how light the image taken through the lens turns out, all other things being equal. High values are important, first of all, when shooting in low light conditions: a fast lens allows you to get a fairly high-quality image without increasing the sensitivity of the matrix, which is fraught with noise and “blurring” of the picture. On the other hand, the actual quality of camera operation (including in dark conditions) also depends on many other factors — the type and size of the matrix, signal processing features, etc. Therefore, aperture in most cases is more of a reference than a practically significant parameter.

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.

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).