Comparison Arsenal 2x24 vs BRESSER National Geographic 3x25

The greatest distance at which a night vision device is capable of detecting individual objects.

The methods by which manufacturers determine this parameter may vary in detail, but the general principle is the same. Usually, the distance is indicated at which, with an illumination of 0.05 lux (a quarter of the moon) and a medium-contrast background, a rather large object can be seen — for example, a human figure with a height of about 170 cm is most often taken. of this object, but only to notice the very fact of its presence. Simply put, a detection range of, say, 200 m means that “something that looks like a person” can be seen in such a device at a distance of 200 m, but individual parts (head, hands) cannot be disassembled.

It is also worth noting that in fact this parameter is highly dependent on the characteristics of the situation. For example, a dark object on a very light background will be visible further, and on a dark one it may not be noticeable even up close; a similar phenomenon is observed for thermal imagers (see "Type"), only regarding the difference in temperature, and not in colours.

The degree of image magnification that a night vision device is able to provide without digital image processing, solely due to the optical system. Such an increase is considered to be preferable to digital, because. it does not impair the clarity of the visible image; and for models based on image intensifier tubes (see "How it works"), this is generally the only available option.

Theoretically, the higher the magnification, the greater the detection range (see above), since a powerful increase allows you to see smaller objects. However, it does not always make sense to chase the maximum performance. The fact is that with increasing magnification, the angular field of view decreases and the minimum focus distance increases (see both below), which can create problems at close range. It is also worth noting that a high degree of magnification adversely affects the luminosity of the entire system — as a result, the actual detection range in complete darkness may be higher for a device with a lower magnification, because. it "catches" more light. Yes, and this parameter affects the cost accordingly.

Note that night vision devices, unlike classical binoculars and monoculars, most often have a fixed magnification. Models with the possibility of smooth adjustment are almost never found, and the only option is to use additional nozzles (see "Form factor").

Now on the market are night vision devices with the following optical zoom: 1x, 2 – 3x, 3.1 – 4x, > 4x

The diameter of the entrance lens that the lens of the night vision device is equipped with.

This parameter is one of the most important for any optical device, including night vision devices: the larger the lens, the more light (or infrared radiation) enters it and the more sensitive the optics are, all other things being equal. The downside of this is an increase in the size, weight and cost of the device. In addition, do not forget that various tricks and additional technologies can be used in the design; therefore, by itself, a large lens is far from always an unambiguous indicator of a high class.

The resolution of the visible image created by the night vision device. Indicated by the number of lines (strokes) per millimetre; the higher this indicator, the more detailed the image is capable of creating the night vision device, the better small details will be visible on it. However such devices will cost accordingly.

In models with an image intensifier tube (see "How it works"), the resolution is highly dependent on the generation of the transducer.

The size of the area visible in the night vision device from a distance of 100 m — in other words, the largest distance between two points at which they can be seen simultaneously from this distance. It is also called "linear field of view". Along with the angular field of view (see below), this parameter characterizes the space covered by the optics; at the same time, it more clearly describes the capabilities of a particular model than data on viewing angles.

The angle of view provided by a night vision device — that is, the angle between the lines connecting the observer's eye with the two extreme points of visible space. Wide viewing angles allow you to cover a large area, but the magnification factor (see above) is low; in turn, increasing the magnification leads to a decrease in the field of view.

The smallest distance to the observed object, at which it will be clearly visible through the night vision device. For normal use of night vision devices, it is necessary that this distance does not exceed the minimum expected distance to the objects in question; thus, it must be borne in mind that the higher the magnification factor (see above), the greater the focus distance, usually.

The offset is the distance between the eyepiece lens and the exit pupil of an optical instrument (see "Exit Pupil Diameter"). Optimum image quality is achieved when the exit pupil is projected directly into the observer's eye; so from a practical point of view, offset is the distance from the eye to the eyepiece lens that provides the best visibility and does not darken the edges (vignetting). A large offset is especially important if the night vision device is supposed to be used simultaneously with glasses — after all, in such cases it is not possible to bring the eyepiece close to the eye. It is also relevant for devices that can be installed on a weapon: the greater the distance to the eye, the less likely it is to get injured due to recoil.

The type of batteries used by the night vision device for operation. Technically, these can be both replaceable elements of a standard size and built-in batteries. However, in fact, the second option is practically not found, because. it does not make it possible to quickly replace a dead battery with a fresh one — and this possibility is critical for most NVD applications.

As for specific types of batteries, the most common options are:

— CR123. The element that has received the greatest distribution among modern night vision devices. These batteries are similar in shape to the popular AA batteries (see below), but their diameter is larger, and their length is noticeably smaller: 17 and 35 mm, respectively. The operating voltage is 3.7 V, which provides good power, sufficient for normal NVD operation. This led to the popularity of CR123.

— AA. Classic 1.5 V finger batteries. The power of such a power supply is lower than that of CR123, which requires more cells; on the other hand, such batteries are easier to find commercially.

— AAA. "Mini finger" or "little finger" batteries, a smaller version of AA cells. Due to their small size, such elements do not differ in power and capacity, and therefore are used only in relatively simple devices for which compact dimensions are important.