Lens diameter
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.
Refresh rate
The frame rate on the screen of the thermal imager (more precisely, on the display visible to the shooter through the eyepiece). The higher this frequency — the smoother and less jerky the image is, the better the thermal imager is suitable for looking at fast moving objects. On the other hand, this indicator directly affects the price of the device and reduces its battery life, because. a high frame rate requires a powerful (and therefore expensive and high consumption) electronic hardware.
Power source
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.
Continuous operating time
The longest time that the device is able to work continuously from fresh batteries without replacing / recharging them. It should be taken into account that manufacturers usually indicate this time for perfect conditions: high-quality batteries, low brightness of the visible image, operation without the use of IR illumination, video output and video recorder (if available, see "Additional"), optimal operating temperature (see below) ) etc. Therefore, in fact, the time of continuous operation may well be lower than stated. Nevertheless, this parameter makes it possible to both evaluate the battery life of individual devices and compare them with each other.
Operating temperature range
Ambient air temperature range at which the night vision device will be guaranteed to maintain normal performance. This indicator is very important, given that such devices are most often used outdoors, where the temperature variation can be very large. Of course, when choosing, you should take into account the conditions in which you plan to work with the device — for example, it hardly makes sense to specifically look for a frost-resistant model for hunting in the summer. But in general, the wider the operating range, the higher the overall reliability of the device, the less sensitive it is to adverse climates.
It is worth noting that going beyond operating temperatures does not necessarily lead to instant failure; however, even with the preservation of operability, the probability of failure increases many times, and such cases are not covered by the manufacturer's warranty.
Weight
The total weight of the night vision device in the working position. If a helmet-mask is included in the kit (see above), its weight, usually, is also taken into account.
The large weight of the device makes it inconvenient to use — both when working with hands and when attached to a helmet-mask. On the other hand, with similar characteristics, lighter models will either cost more or have poor quality materials.
