Let’s begin by discussing the differences between the two types of night vision.
Image Intensifiers are more commonly referred to simply as “night vision.” For the remainder of the article, I will refer to image intensifiers as “night vision.” Night Vision uses a powered image intensifier tube to produce a light-amplified image to the user. The tube literally amplifies existing ambient light to produce a bright, detail-rich image. Traditional night vision produces a green image to the viewer. Green is the most visible color to the human eye. We can see more shades of green than any other color in the visible light spectrum. As such, the green phosphor screen in the image tube presents the most hues and shades to the user, allowing him/her to best resolve the image in detail and depth. This is an important positive capability in that night vision users can see into the dark and gain positive identification of their surroundings and targets.
Since night vision is simply allowing you to see in the dark, it is completely possible to achieve positive identification of faces, clothing, animals, etc. This is perhaps the most important aspect of night vision. Since night vision devices are mostly used in conjunction with a firearm, the ability to achieve 100% Positive Identification (PID) is critical before taking a shot. Night vision will allow the user to read signs as well. Another important aspect of night vision is that it allows for easier depth perception while moving. Because the tube is amplifying existing ambient light, shadows and terrain undulation can be more easily identified. This helps night vision users to gauge distance using terrestrial association. The key benefit to night vision is its identification capability.
However, despite the benefits of night vision, it is not a perfect tool. Like our eyes, we are susceptible to being fooled by camouflage. Nature has the ability to camouflage people, animals, and objects simply by placing foliage in front of them. Sometimes, possible targets will go out of their way to camouflage themselves in the terrain. Bad guys can wear camouflage clothing and attach foliage to their person. Animals often have natural camouflage in their coats. The same camouflage that works for a person or animal during the day will work just as well, if not better, through night vision (after all, the image is the same as normal, but now being presented in a single color palette).
Night vision may also be slightly harder to use during inclement weather conditions such as rain, snow, fog, and smoke. Another, more obvious, deficiency in night vision is that it only works at night. However, we have to remember that night vision requires some amount of ambient light to function. Today’s Gen3 tubes can do much more with much less light, we still need to have some illumination to gather. If you take a brand new Gen3 device into an absolute pitch black environment, you will not have any image. At that point, an external infrared illuminator is required.
Thermal imagers work differently than night vision. Rather than amplifying the existing light in an image, thermal uses a special detector that senses infrared energy. Infrared energy is produced by everything in the world, whether natural or man-made, and increases as its heat rises or it produces friction. So essentially, thermal imagers detect heat, providing a starkly contrasted image where heat-producing targets and objects will light up against their cooler surroundings. This trait makes thermal imagers ideal for detecting targets in the user’s environment. The most obvious use for thermal devices is easy detection of targets in the field. The warmer an object is, the brighter it will appear in the thermal device. An animal or person that is hiding among foliage will more easily be spotted against the landscape since the user is not depending on the shading and tones of the target for detection.
Detection is the most important aspect of thermal imagers. These devices will allow users to quickly detect the presence of a possible target against a wide range of landscapes. Thermal imagers can also be useful in tracking blood trails and, depending on the time lapse; foot prints. This can be useful in finding suspects or animals. Thermal is also capable of seeing through light rain, snow, fog, and smoke. Another positive trait for thermal devices is that they can be used during the day. Night vision will eventually become damaged when exposed to too much light for extended periods of time. Thermal devices can operate regardless of the ambient light present. This includes high noon or absolute pitch black. Though, thermal devices do tend to work better at night because the ambient environment will have cooled down, increasing target contrast.
While thermal devices excel at detection, they are not as useful for identification. It is possible to get a decent level of identification capability out of a thermal if it is a high resolution system (such as 640×480). However, facial recognition and PID is not generally possible. Thermal is also incapable of reading text printed on a flat surface. This is most easily demonstrated by looking at a sign or a garment. If the letters are raised or have a different finish than the rest of the surface, it may be possible to make out the graphic, but you will not get nearly the legibility of night vision.
Positive Identification is perhaps the biggest drawback to using thermal. Obviously, the higher resolution systems will be able to resolve more detail in an image. However even they are going to be lacking in the ability to clearly identify someone’s face or one type of animal from the next. From a professional standpoint, this means that identifying an armed suspect from an armed officer is going to be more difficult. For hunters, it can make it more difficult to tell the difference between a coyote and dog. Though, we can surmise differences in our thermal targets by observing their movement and behavior, it is important to remember that we are most often dealing with firearms in conjunction with these devices. Once the trigger is squeezed, the possible outcome is the loss of a life. The consequences of mistaking a calf for a hog can be a $13,000 bill from the ranch owner. The consequences of mistaking a good guy for a bad guy can mean life in prison. And the consequences of mistaking someone’s dog for a coyote can mean the dog’s owner hunting you down.
The issue is exacerbated at distance since electronic zoom cuts the image resolution every time. Thermal imagers are also incapable of seeing through glass. Because of this, their lenses are made from an expensive material called germanium. But this limitation can be detrimental to surveillance operations, or if a hunter wants to observe the field from his/her vehicle cab. One last thing to consider with thermal imagers is the video frame rate. Thermal imagers are active systems that provide the user a video on an OLED screen to view through the eyepiece. So unlike night vision, a user does not look “through” thermal and see the world. Real time video runs at 60 Hz and some thermal devices display at this frame rate. But, most thermal units run at 30 Hz. This means that the video image you observe can experience some slight clipping during fast movements.
Again, the above information is a simplistic overview or the characteristics and pros/cons of night vision and thermal imagers. Depending on the device you possess, some of the characteristics can vary. Now that we have established a baseline idea of the capabilities present in these devices, let’s take a look at how they are applied to some practical scenarios.
We chose to bias these videos towards the first-responder market. We felt they would best display the capabilities of the various night vision devices in different environments and could be easily juxtaposed across the hunting and military markets as well. No live firearms were used in the production of these videos. Also please note that filming through night vision devices is incredibly hard to do because the focus of the night vision device and the camera are not always in perfect sync. We did our best to provide as accurate a representation as possible.
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See Scenario 1 Here
See Scenario 2 Here
See Scenario 3 Here