Jahnke NSV Kompakt 1x48

IIT Generation

IIT stands for image intensifier tube which is used to amplify low light level images in a wide light spectrum. It’s a special Image Intensifier Tube (IIT) built in every analog night vision device and it is the heart (most important part) of every night vision device. Quality of image intensifier tube determines in which category or generation night vision device will fall. The higher the quality of IIT technology, the higher the generation. There are 4 IIT Generation (gen) of night vision devices, but due to generation 0 nobody produces (because technology is very old and not effective enough), there are 3 generations on the market.

Generation 0

Before generation 1 there was generation 0 back in the earliest years of 1950. Those night vision devices were based on image conversion rather than intensification and that was the reason they required an IR illuminator (click the info button for IR illuminator wavelength to get to know what IR illuminator means). Generation 0 typically did use an S-1 (photosensitivity of 60 uA/lm) photocathode, which required high voltage to work and get an optimal image. Companies do not produce them anymore, due to this being an old technology that provides a bad image and high geometric distortion. The system of generation 0 also usually failed when exposed to bright light sources, due to not having sophisticated electronics that provides Bright-Source Protection (BSP) or bright light cut off.

Generation 1

First generation night vision (GEN 1 NV) devices were invented in the 1960s. Some of them had 3 photocathodes in the system, because of that, they were heavy and bulky. The prices of gen 1 are now low, but for this, you get an image that is clear at the center but distorted or blurry around the edges. Gen 1 devices use an S-20 photocathode (photosensitivity of 180-200 uA/lm). They also need (like gen 0) high voltage to work properly but provide higher photosensitivity. These were the first truly passive image intensifiers. Gen 1 is also known for geometric distortion and fails when exposed to bright light sources (like gen 0 it doesn't have BSP). The performance is poor at low light levels, but, you can get a brighter image when adding additional IR illuminator, which also means, you will be visible to other night vision users. With a good IR illuminator detection range is around 100 m. Gen 1 can easily be damaged, if they are used in daylight, so the user has to take care not to switch the device ON without the lens cover. A sudden bright light source can also damage GEN 1 night vision device. Consider this, even with the lens cover on it is still not recommended to have the device switched ON for a longer time. The gain (This is the number of times a night vision device amplifies light input) is typically from 500 – 2000 times. Gen 1 NV devices normally (when pressing the OFF button) don’t turn OFF immediately, but will provide an image for a longer time. These NV devices are most commonly used by civilians and are suitable for the most application. The price/performance is relatively good.

Generation 2

Second Generation Night vision (Gen 2) devices were developed in the 1970s. Inside the system, there is a sophisticated microchannel plate and electronics. Because of this, image quality is much better compared to gen 0 and 1. And the size of night vision devices is smaller. All of the newer gen 2 devices have built-in BSP or bright light cut off. This provides an automatic adjustment in different light situations and protects the photocathode from damage. Gen 2 typically uses an S-25 extended red photocathode (photosensitivity 240+ uA/lm). They provide a good performance in low light situations and provide low image distortion. With an additional IR illuminator, you can get even better image quality. Generally, Gen 2 NV is more sensitive than the Gen 1, which means, you see further and the image is brighter in dark conditions. Even the clarity is improved against Gen 1. Normally Gen 2 can be used without IR illuminator but in very dark areas it is a good accessory to have. The system gain for Gen 2 devices is from 10.000 – 20.000 times. The newer Gen 2+ have a gain value of even 25.000 – 45.000 (photocathode Photonis XR-5).

Generation 3

Gen 3 has two big differences against gen 2. The main improvements are high-quality gallium arsenide (GaAs – it’s a compound of the elements gallium and arsenic) photocathode and ion-barrier film on the microchannel plate. GaAs photocathode enables detection of objects at greater distances under much darker conditions then Gen 2 or lower generation night vision devices. Ion-barrier filmed microchannel plate provides an increase of the operational lifetime of photocathode up to 10000 hours and more. Gen 3 devices use high-quality photocathode with photosensitivity of over 800 uA/lm. For Gen 3 devices you don’t need an additional IR illuminator. If we put everything together, shortly written, Gen 3 devices provide excellent performance in low light situations without perceptible distortion and with a long photocathode lifetime. Sure they also have BSP and all other features with lots of improvements from Gen 2. The gain is from 40.000 – 65.000 times.

These are only the main IIT Generations. There are also generations like gen 1+, gen 2+ and different quality photocathodes inside generations. Again, many times heard, the higher the quality the higher the price.

Source: AR15 (Gen 2 vs Gen 3)

Introduction

Magnification is an optical parameter which enlarges/zooms the viewing image and makes the observed object seem bigger. For example, with magnification factor 10 we see objects 10 times larger, which means if an object is 0.1 m high and 100 m away we see it 1 m large. In other words, it’s the same observing the object that's 100 meters away with a 10x binoculars as watching it with the naked eye 10 meters away. In choosing the right magnification for fixed magnification optical products, practice shows that the most useful magnifications are between 7x and 10x, where average people seem to handle optics without too much hand tremor.

Source: ZEISS

Fixed magnification

Optical products with fixed magnification are designed in a way that they allow only one magnification of a viewing object. Due to a smaller number of lenses used in their construction, they are optically brighter and have lower loss of brightness. The number of lenses contributes to its smaller size and lighter weight in comparison to optics with variable magnification. Most of binoculars tend to have fixed magnification, whereas with riflescopes it’s getting rarer each year. Normally this kind of optical products are easier to use and cheaper. They also offer better optical performance, especially in terms of light transmission rate.

Variable magnification

Variable magnification simply means that the optical product is designed in a way where you can change magnification of a certain area. This consequently changes the viewing angle, where higher magnification means smaller/narrower viewing angle and lower magnification means wider viewing angle. Variable magnification adds to versatility and general usefulness.

Optics Trade debate about Fixed and Variable magnification

Lens diameter

Lens diameter represents the second value in product’s name/designation. For example, 10x42 optics have 42 mm diameter of the lens at the front (those that are closer to the viewing object). It is known that the bigger the lens, the more light goes through and the image we see is brighter. All of this, however, depends on the magnification and quality of a certain optical product. Although the bigger lens diameter in binoculars is better, the size adds up on the weight, making it more heavy and difficult to handle. With riflescopes, bigger size of a lens diameter also means more problems with mounting.

The most common lens diameters are 24 mm, 42 mm, 50 mm and 56 mm.

Source: ZEISS

Exit pupil

Exit pupil is a circle from which the light is being transferred to your eye through the optical product. When you holdthe optics a bit far away from your eyes towards a light, exit pupil can be seen as a bright circle in the center of each eyepiece. The larger the exit pupil the more light can reach the eye and the image appears brighter. This is why exit pupil plays an important part in the optical products in poor light conditions at dawn or dusk. Size of the exit pupil also determines how comfortable viewing through an optical product really is. An important factor is also the size of the eye box, which is a space where the eye still has an entire picture, without any tunnel vision or blurry edges. Bigger eye box means more flexibility of the eye position and therefore more comfortable viewing, because the eye can move in several directions within the eye box and still obtain a full image.

Source: ZEISS

The diameter of the exit pupil is calculated by dividing lens diameter with magnification. E. g. 8x50 binoculars have an exit pupil in the diameter of 6.25 mm.

To ensure a brighter image, the eye pupil in low light conditions has to be at least as big as the exit pupil. This way there’s no loss of light and the image is as bright as possible. However, the maximum diameter of the eye pupil depends on age. At night, children’s eye pupils can widen up to 7 mm, while with aging they decrease to a maximum of 4 mm. So if the viewer’s pupils can only be open up to 4 mm, the 7 mm exit pupil cannot be fully utilized. It may contribute to more comfortable viewing, but not to brighter image.

Source: ZEISS

In daylight, when the eye pupil is open up to 3 mm, all the optics with exit pupil bigger than 3 mm are equally bright. For example, the 8x30 binoculars with 3.75 mm exit pupil are no brighter than 8x56 binoculars with 7 mm exit pupil. Those with 7 mm are however more comfortable to use, since they’re less sensitive to the eye position (they have bigger eye-box).

Eye Relief

The only way of obtaining the whole field of view is to have the right distance between the eye and eyepiece – referred to as the eye relief. The eye relief is not necessarily a decisive factor in choosing the right optical product, however it is a useful information if you wear glasses. The eye relief then should be at least 16 mm for comfortable viewing and getting a complete image. Binoculars with too short eye relief give people with glasses a tunnel vision and only show the middle part of an image. With riflescopes the optimal distance is 90 mm or even more for safety reasons (recoil).

Without glasses the distance when using binoculars should be minimum of 15 mm, although everyone has a preferred placement as long as they’re obtaining complete field of view with no blurry edges.

Most binoculars have movable eyecups, where you can adapt them to fit different face structures (if your eyes are further away from you nose etc.) and therefore maintain a steadier grip. If you wear glasses, the eyecups should be closed down so you can lean them onto your glasses.

Source: ZEISS

Field of view

Field of view is an area you see when looking through the optical product. Although it primarily depends on the build of the eyepiece, it is hugely affected by magnification. If you look through two binoculars of the same model but with different magnification, you can see that the one with lower magnification factor will have a wider field of view. So when comparing binoculars, you must compare the ones with the same magnification. With riflescopes the field of view is being measured at 100 m, while with binoculars, spotting scopes and other optical products it's measured at 1000 m.

With binoculars a field of view with more than 140 m at 1000 m distance is considered a wide angle, while with riflescopes it is with a field of view over 38 m at 100 m. Wide angle is particularly useful in bird-watching.

It is also important to mention that the size and lens diameter of optical products are not indicators of their field of view - bigger housing doesn’t automatically mean wider field of view.

Field of view can be expressed in two values – degrees or meters.

Degrees:

One degree is 17.5 m at 1000 m / 1.75 m at 100 m.

If you divide the field of view given in meters by 17.5 you get the field of view in degrees.

Meters:

If you multiply degrees with 17.5 you get the field of view at 1000m.

Source: Lovec

Field of view

Field of view is an area you see when looking through the optical product. Although it primarily depends on the build of the eyepiece, it is hugely affected by magnification. If you look through two binoculars of the same model but with different magnification, you can see that the one with lower magnification factor will have a wider field of view. So when comparing binoculars, you must compare the ones with the same magnification. With riflescopes the field of view is being measured at 100 m, while with binoculars, spotting scopes and other optical products it's measured at 1000 m.

With binoculars a field of view with more than 140 m at 1000 m distance is considered a wide angle, while with riflescopes it is with a field of view over 38 m at 100 m. Wide angle is particularly useful in bird-watching.

It is also important to mention that the size and lens diameter of optical products are not indicators of their field of view - bigger housing doesn’t automatically mean wider field of view.

Field of view can be expressed in two values – degrees or meters.

Degrees:

One degree is 17.5 m at 1000 m / 1.75 m at 100 m.

If you divide the field of view given in meters by 17.5 you get the field of view in degrees.

Meters:

If you multiply degrees with 17.5 you get the field of view at 1000m.

Source: Lovec

Apparent field of view (deg.)

The apparent field of view is a value in degrees that represents the viewing angle of an image you see through the eyepiece. Two binoculars that share the same magnification, lens diameter and field of view don’t necessarily have the same apparent field of view, because it depends on the structure of the lenses inside an eyepiece. It’s simply a subjective impression of the field of view.

Apparent field of view is also depending on the eye relief distance. Shorter eye relief means wider apparent field of view. But if comparing two different binoculars with the same eye relief, the one with the larger eye lens in the eyepiece will have larger viewer field.

It can be calculated by multiplying the actual field of view with the scope’s magnification. Higher value is better as it makes the image appear wider and bigger.

Source: Nikon

Closest focus distance

Closest focus distance is an important value when watching butterflies, moths or plants at a really close distance. It represents the nearest distance where the viewing object can still be in focus. With binoculars, an excellent viewing distance is from 1.5 m below. If you’re not particularly interested in watching objects at a close range this is an irrelevant factor when choosing a new pair.

Min. Resolution

Before getting to know what resolution stands for, you need to know what “ lp / mm “ means. It means line pairs per millimeter (lp / mm). This units are used for measurement of image intensifier resolution. How close lines can be to each other and still be visibly resolved, this determines the quality of resolution. Line pairs are composed of a dark line and the nearest bright line. A line can be dark or bright. For example, a resolution of 20 lines per millimeter means that 10 dark lines and 10 bright lines are alternating or 10 line pairs per millimeter (10 lp / mm). The more line pairs the better the resolution the higher the price of a product. The best night vision optics on the market offer resolution with 64+ lp / mm.

Tube resolution is measured in line pairs per millimeter (lp / mm), system resolution is measured in cycles per milliradian (cy / mr). Tube resolution is important, if you are comparing the quality of optics and filters. Mostly resolution is measured at low-light and high-light conditions. Optimal resolution should be determined at point between very low-light and very high-light conditions. Image resolution (lp / mm) will remain always the same, while the system resolution (cy / mr) is affected by altering eyepiece or objective and with adding relay or magnification lenses.

Minimal resolution is a parameter measured at lowest light conditions.

If we put everything together, when comparing different night vision optics, the higher the price, the higher the quality, which determines the ability to present a sharp image. Notice also, night vision with lower resolution will maybe produce good results in higher night-light conditions with more ambiance light, but performance in darker conditions will not be so good.

Source: AR15

Max. Resolution

Before getting to know what resolution stands for, you need to know what “ lp / mm “ means. It means line pairs per millimeter (lp / mm). This units are used for measurement of image intensifier resolution. How close lines can be to each other and still be visibly resolved, this determines the quality of resolution. Line pairs are composed of a dark line and the nearest bright line. A line can be dark or bright. For example, a resolution of 20 lines per millimeter means that 10 dark lines and 10 bright lines are alternating or 10 line pairs per millimeter (10 lp / mm). The more line pairs the better the resolution the higher the price of product. The best night vision optics on the market uses resolution with 64+ lp / mm.

Tube resolution is measured in line pairs per millimeter (lp / mm), system resolution is measured in cycles per milliradian (cy / mr). Tube resolution is important, if you are comparing the quality of optics and filters. Mostly resolution is measured at low-light and high-light conditions. Optimal resolution should be at point between very low-light and very high-light conditions. Image resolution (lp / mm) will remain always the same, while the system resolution (cy / mr) is affected by altering eyepiece or objective and with adding relay or magnification lenses.

Maximal resolution is a parameter measured at highest light conditions.

If we put everything together, when comparing different night vision optics, the higher the price, the higher the quality, what determine the ability to present a sharp image. Notice also, night vision with lower resolution will maybe produce good results in higher night-light conditions with more ambiance light, but performance in darker conditions will not be so good.

Source: AR15

Gain

Gain is an information, that tells you the number of times a night vision amplifies the ambient light. The image intensifier is the heart of all analog night vision devices and it is the main component. Effectivity of the intensifier is measured with “gain”. The older Gen 1 night vision devices have a GAIN from 500 – 2000 times. The gain for Gen 2 NV devices is typically from 10.000 – 20.000 times, and there are Gen 2 NV devices with different photocathode options on the market that even exceeds those values. Gen 2 with higher quality photocathode falls into Gen 2+ night vision category, which GAIN value is 25.000 to even 45.000 with the newest photocathode Photonis XR-5. The gain on Gen 3 NV devices is from 40.000 to 65.000 times.

The bigger the gain, the bigger amplification of the ambient light, the brighter and better quality image you will get and of course, the higher the price.

Range of detection

One of the first questions when buying night vision optics is »How far will I be able to see?«
The range of detection is the distance on which you can detect/see a 1.7 m high object.

Always have in mind that there are many different things that influence how far you can see looking through night vision optics. For example, if the object is larger it`s easier to see. Another outside impact is lighting condition, the more light reflecting from the moon, stars (ambient lights), the further and also better you will see. The range of detection is given at average conditions.

The range of detection also applies to digital night vision and thermal imaging devices.

Source: Armasight

Bright Light Cut-off or Bright Source protection (BSP)

The newer generation and newer night vision devices have build in special electronics that lower the power or reduce image brightness when sensors detect sudden bright light such as flashlights, car headlights and other devices that causes bright light. Otherwise, without bright light cut-off possibility sudden appearance of bright light could damage the image tube and shorten its life span.  

Second and third generation of night vision devices have also build in automatic image brightness. This possibility enables automatic adjustment when even smaller amount of sudden bright light occur and also enhances devices lifetime. It also helps to protect of sudden appearance of bright light  and prevent damage of night vision device.

Source: Careflight (NV with no BSP and with BSP)

Bright Light Cut-off or Bright Source protection (BSP)

The newer generation and newer analog night vision devices have build in special electronics that lower the power or reduce image brightness when sensors detect sudden bright light such as flashlights, car headlights and other devices that causes bright light. Otherwise, without bright light cut-off possibility sudden appearance of bright light could damage the image tube and shorten its life span.  

Digital night vision devices do not have such a protection, because the light which enters the device comes on a sensor and not into an image intensification tube which amplifies the light input. The sensor in a digital night vision device is not sensible for sudden bright light, even if it's turned on at daytime.  

Second and third generation of night vision devices have also built in automatic image brightness. This possibility enables an automatic adjustment when even a smaller amount of sudden bright light occurs and also enhances devices lifetime. It also helps to protect against a sudden appearance of bright light and prevent damage to a night vision device.

Source: Careflight (NV with no BSP and with BSP)

Auto –TurnOff

Some of the red dots and rifle scopes with reticle illumination have Auto – TurnOff function. This means, in case that you forget to turn off illumination or when you leave your firearms on table (you don’t do any movements with rifle scope), illumination automatically turns off. The time when illumination turns off is different from rifle scopes to rifles scopes.

Many of the expensive and high quality rifle scopes with illuminated reticle have an Auto-TurnOff smart motion sensor that detects different angles and automatically turns OFF or even ON the illumination of the reticle, based on the rifle scope position.

This is a nice feature to have, because this increases the battery life. 

Source: Swarovski

IR Illuminator wavelength

Before explaining IR illuminator wavelength, you need to know what is the meaning of these words separately.

The visible spectrum is a part of the electromagnetic spectrum, which is visible to human eyes.
Electromagnetic radiation in this area of wavelengths is called visible light or simply light – measured in nanometers (nm).
IR or infrared light has slightly longer wavelengths than the visible light, and that's why it is not visible to the human eye.

The visible spectrum of human eyes is somewhere between 400 and 700 nanometers (nm) wavelength, while infrared is over 750 nm, which is outside of the visible spectrum of human eyes. That means that our human eye cannot detect an infrared source (its invisible to our eyes). Night vision devices can detect IR light because they work on wavelengths over 750 nanometers. So infrared Illuminator provides light over 750 nm wavelength.

There are 2 different types of IR illuminators – LED or laser and 2 types of night vision devices – analog or digital. This is very important to know when buying the right IR illuminator for your night vision device. Different IR illuminators provide light with a different wavelength and they work better on each type of night vision devices.

The main difference between analog and digital night vision device is that digital type works with all wavelength ranges, but analog works only under around 900 nm wavelength.
Laser IR illuminator wavelength from around 780 nm to 810 nm works fine on generation 1, 2, 3 and digital night vision devices, but the problem is that some animals can detect wavelength up to 850 nm. Because of that, IR illuminators with a wavelength up to 810 nm are not recommended for hunters.
Laser IR illuminators with a wavelength of 850 nm don’t work properly with generation 1 night vision devices, because they work on wavelengths till 800 nm. Whatsoever, they work well with gen 2, 2+ and Gen 3 night vision devices. IR illuminators with wavelengths from 850 nm upwards are suitable for hunting purposes.

Laser IR illuminators with wavelengths from 875 till around 910 nanometers work with some high-quality Gen 2+ night vision devices, Gen 3. and also digital night vision devices. Everything that is above this wavelength is designed only for digital night vision devices.

Pulsar F155 (IR illuminator)

Filled with

Optical products are often filled with dry gas to prevent the condensation on the inside of the housing when exposing them to temperature extremes. If there is even a slight sign of air inside, there is a certain % of moisture present. Usually they’re filled with either argon or nitrogen gas, which have the same effect – to prevent the moisture and internal fogging without affecting the optical properties. In addition, these gases also prevent the formation of fungus which would destroy the optics. Internal dewing was the biggest problem in older binoculars when exposed to lower temperatures, because they weren’t watertight and contained air. Newer binoculars are therefore all airtight and filled with dry nitrogen or argon.

Waterproof

The waterproof feature is made to keep the optical products sealed and protected from water or dust. Such products are suitable for marine, hunting, hiking or in extreme humidity. Even if you’re not planning on using them in this kind of situations, it is a good feature to have in case of heavy rain or dust. Waterproof optical products are typically sealed with O-rings.

All optical products that are fogproof are also waterproof because they have to be properly sealed to keep the dry gas inside. Yet not all waterproof products are also fogproof as the air inside the product is not necessarily replaced with dry nitrogen or argon.

You should be careful not to confuse waterproof with weather-resistant as they’re designed to protect only against light rain and are not fully sealed.

Slightly better waterproofing of binoculars can also be ensured with an individual eye focusing mechanism, due to less moving parts than with the central focusing system.

Fogproof

Fogging in optical products can occur when you move them from the warm insides of your house to the cold outdoors. To prevent the formation of inside fogging they’re often filled with dry gas – either nitrogen or argon which contain no moisture.

To keep the gas intact on the inside, the optics have to be properly sealed, which is why all fogproof optical products are also waterproof.

It’s important to keep in mind that fogproof means that it’s to prevent fogging on the inside of the optics, not on the outside. If your outside surface of the lenses fogs up due to temperature differences or humidity just allow them to adjust back – do not wipe the condensation off as it can be damaging to the glass surface and its coatings.