NIGHT VISION uses modern technology known as Image Intensifier Tubes (IIT's) to amplify existing light to produce an image which can be seen by the human eye, many of such lights are in the INFRARED spectrum. These tubes are analog and show exactly what you are looking at in real time, they do not use cameras or anything of the sort. There exists digital systems, such as Night Vision cameras, which can be fun to play around with however for the average person, the technology we have access to is currently not sufficient enough to produce a usable image in most conditions, without supplementary infrared lighting or illumination. Image intensifier tubes amplify all light, and therefore are not magic. If there is no light, then there is also nothing for the tube to see, therefore nothing for you to see.

INTENSIFIER TUBES are the heart of all analog night vision devices and are usually the make or break on whether a unit can be considered good, average, or bad. There are many factors to take into account when purchasing a night vision device, most of which derive from the specifications of the image intensifier tube the unit comes equipped with, or that you are choosing. Let's discuss that.

TUBE SPECIFICATIONS are usually provided by a seller in means of a data sheet, which contains measurements taken by the factory upon completion of the tube assembly. Different generations of image intensifier tubes have different thresholds of values.

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The most common way to measure a tube's performance is by using an equation referred to as the FIGURE OF MERIT (FOM). FOM is equal to Resolution x SN/r. When choosing a unit, it is important to consider which FOM value you want, as it will generally dictate it's performance. It is also important to request specification sheets if possible, which is a part of our HAND SELECT process, this is due to wanting a balance between Resolution and SNR. Most users will not be able to tell the difference in increments of 100FOM, however at 200 and above the difference is quite notable. Resolution is measured in LINE PAIRS PER MM (lp/mm) which is shown below. It is the tubes ability to contrast the difference between pairs of white and black lines in varying sizes in low light conditions. The more lines the tube can see, the higher the resolution. Signal to noise ratio is the amount of noise (fuzz) in the tube. As well as FOM, Gain is also an important metric to consider, as it will indicate the brightness of your tube. EBI and Halo are also very important to most users. EBI is Equivalent Background Illumination, which is kind of like when you turn on a TV and it displays that black fuzz. Halo is the size of light sources, for example if you have a tube with a high Halo, street lights will have a large glow around them, whereas lower halo tubes will be smaller. Lower EBI, lower Halo tubes are important specifications to look for when purchasing.

IN SUMMARY: Look for: Low Halo, Low EBI, High Gain, High Resolution and High SN/r.

GENERATIONS OF IMAGE INTENSIFIER TUBES are classified by the limitations of technology used to create a tube. You will see Generation 2+ and Generation 3 image intensifier tubes for sale most frequently. Most buyers will immediately assume that because Gen3 is the highest, it is automatically better, however this is not exactly true. Whilst Gen3 IIT's can be better, it is usually dependent on the situation which the device will be utilized. For example, Gen2+ tubes have lower gain and are therefore less sensitive to light and protect themselves better, which is useful for urban environments or areas with high light pollution. However, Gen3 tubes have superior gain therefore making them more useful in areas with extremely low light. This does not mean that either are useless in their weak areas, both generations of tubes will perform very well in both conditions if specifications, such as Resolution, Signal to Noise Ratio (SN/r), Halo and EBI are similar. It is important to note, that whilst Gen3 tubes will outperform Gen2+ tubes in low light conditions, the images produced by Gen3 in a situation where Gen2+ cannot see anything, is usually not far better. There are good comparisons on YouTube showcasing the differences in IIT in varying light conditions.

PROTECTIVE FEATURES OF AN IMAGE INTENSIFIER TUBE includes autogating, bright source protection (BSP) and automatic brightness control (ABC). At a very minimum, all image intensifier tubes have BSP and ABC, this allows tubes to protect themselves when pointed at brighter lights such as a full moon, street lights, flashlights etc. Autogating is the process of a tube lowering the voltage supplied to it when it has higher amounts of light entering, such as when a light is turned on, the tube will decrease voltage to protect itself from damage. These protective features also allow tubes to guard themselves from muzzle flash, explosions and lasers. A tube will be damaged from bright lights if it is exposed to them for a prolonged period of time, for example, you forget to turn off your goggles and leave them pointing at a car's headlights. You will then notice defects such as blemishes or ghost images, which we delve into below.

It is always the buyer's responsibility to ensure their goggles are always protected from bright lights, as to avoid any potential damage. It should be noted that the brighter the light is, the faster it will damage your tube. Even if a tube is powered off, if the lenses are not covered, light can still enter the tube and cause damage. Always be sure to cover your lenses and remove your batteries when you are finished with your goggles, to ensure they do not become damaged.