Scot’s Product Review: FLIR LS-Series Thermal Imaging Camera


Seeing in the dark is something we poor humans aren’t good at. The term “cover of darkness” is an apt description, and if we can penetrate it we have a serious advantage over those who can’t. This also applies to anything that obscures visibility, such as smoke, haze, or other obstructions. We often hear the buzz phrase “force multiplier”, and anything that helps us see when our opponent can’t is a big one in my book. Being able to detect attackers first or control our own people is pretty huge, as the perils of being clueless are obvious. Besides the “golly gee whiz” factor of getting play with this sort of equipment, I thought it important to discuss how useful this technology could be to preppers as well as how dangerous it is if the wrong folks have it.

There are basically two technical strategies to seeing in the dark. One depends on the light reflected from the target. The Gen I, II, and III night vision devices we see advertised are of this type. They allow us to see short wave infrared (SWIR), also called near infrared. This is a form of light that is just outside our ability to perceive it. An image intensifier can convert it into visible light that we can see in a night vision device. Gen III units also show us a bit of visible light. Since we are seeing reflected light, the target has to be lit by a light source for us to perceive it. The earliest units required an infrared floodlight. The newest and most expensive models will let us see with the help of moonlight, starlight, or even the glow from city lights reflected from low clouds. While each successive generation requires less and less SWIR light reflected from the target to allow you to see it, if someone is in a shadowed area or it is a cloudy night away from all other lights, you won’t be able to see them, even with the best unit, unless you shine a SWIR light on them. This has obvious disadvantages. Your light, at worst, is going to be a bullet magnet if a hostile also has this sort of night vision.

The military PVS-14 is a commonly seen example of this sort of gear. They provide the green image we often associate with night vision from having seen it on the news.

Then there are thermal units, like the FLIR LS I am writing about in this review. It is made by FLIR Systems, Inc. It detects the long wave infrared (LWIR) or far infrared energy emitted by all objects. It sees heat, in other words. Since it is detecting emissions and not reflections, it is completely passive and won’t give you away. Further, it can detect objects in total, absolute darkness, which is a pretty amazing feat. You have probably seen a lot of this type of imaging on TV when you watch terrorists targeted by aircraft or police chases from helicopters. What makes this work so well is that animals (other than reptiles and the like) are almost always a different temperature than their surrounding terrain.

Unlike SWIR imagers, the LWIR ones can be helpful in spotting targets in daylight. It can make it far easier to see an animal or person in foliage or through haze, even if they are wearing good camouflage. You see them as a very bright object against the background.

This video can help show some of the differences between thermal and SWIR night vision equipment. The people who made it appear to be vested in LWIR technology, so they do stress the advantages.

Thermal imaging is becoming more and more popular in law enforcement and units like the one I am reviewing are small and light enough to carry easily. It weighs less than a pound and is under seven inches long and about 2.5 inches in diameter (though it isn’t perfectly round). It has a built-in lithium ion rechargeable battery that gives about five hours of service. It charges with a USB cable. The only drawback is the cost, which starts at about $5,000.

These devices usually provide a black and white image, but they can add color to indicate the temperatures of objects in the field of view. One helpful trick with this one is that you can tell it to display hot things as lighter than cooler things or reverse it and have the hot things dark. Depending on the background, changing the view might make it easier to see targets. You can adjust the settings for how bright to make certain temperatures. You can also tell it to show things above a certain temperature as red, which could help make animals pop out even better when you are scanning with it. A FLIR Systems video will show how some of these options work pretty well.

It is possible to defeat SWIR units, like the PVS-14, with good camouflage and maintaining awareness of surroundings. If you stay in the shadows and avoid being silhouetted against the sky or a bright background, it is far harder to be spotted. The only way to see into deep shadows with this equipment is to use an infrared illuminator, which will give you away. Interestingly, some fabrics and how they are laundered can make you much more visible. The fabric brighteners and softeners that make your clothes look clean also make you more visible under IR. It would be best, if you worry about this, to look for some of the special detergents used for hunting clothes that don’t have the brighteners or softeners.

I think thermal imagers are far tougher to defeat than SWIR devices. The best way appears to be putting something between the imager and yourself that blocks your heat radiation. That part isn’t very hard. The problem is that if you block yourself with something that does not blend in with the surroundings, you will create a suspicious anomaly that can attract attention. First, your screen has to be at about the same temperature as the surroundings or it will show. It also has to have the same heat texture as the surroundings. Just as light reveals texture to our eyes, thermal energy exposes a texture that shows up in the thermal imager. A material that is very uniform, as a man-made object might be, is going to look suspicious. If it has straight edges, they could also attract attention as there are few truly straight lines in nature. Further, everything in nature is constantly changing temperature over time. It gets hotter as the sun goes up and cooler as it goes down. If your screen gives up or absorbs heat at a different rate than its surroundings, it can expose you. Your cover could also absorb your own heat and reveal you that way.

There is camouflage clothing intended to defeat thermal night vision. While it is clearly a major help, it is still possible to see the camouflaged subjects using LWIR equipment. They no longer show hot spots; instead, they show as dark blotches that don’t belong in the scene. An alert operator will be curious about that. Since camouflage clothing has to trap your radiant heat it will have drawbacks in hot climates. If you are moving and you change to a warmer or colder location, it has to be able to adapt to it quickly or you will standout. When you are standing, it will not necessarily be the same temperature as what’s behind you. I am trying hard to stress the difficulties of dealing with this. We can pretty much make ourselves invisible to normal vision without much trouble, and with some knowledge and care we can disappear to SWIR devices, but this thermal stuff is far more complex of a problem. Some materials that offer good blocking of thermal energy, like aluminum foil, are highly visible to even the Mark I Eyeball. We now have a three-way problem– normal vision, SWIR, and thermal– to defeat.

I’ve heard suggestions for using diversionary devices, like flares or fire bombs, to blind thermal imagers, but they appear to regain their sight fairly quickly. When you move out of the bloom from the fire, you will show up. If the enemy has an area weapon, they could just target the bloom. A better plan would be to hide amongst something, like a herd of animals, but those aren’t always available. A city will certainly offer more options than the countryside. I was not able to verify it, but different types of foliage appear to offer varying degrees of concealment. Learning which is best could be helpful. Hiding under a car could also help, especially if it was warm from driving.

There are units that can blend visible and thermal images, which will provide more details for the observer. These are showing up in light aircraft, and the results are impressive http://ww This corrects one of the startling features, to me at least, of the LWIR units. You cannot see visible light in the display. This means someone can be walking about shining a flashlight and you can’t see them through the unit. If a light doesn’t make much heat, you won’t even be aware of it. The blended view gives you both. Some units blend visible, thermal, and SWIR into the same display and also allow you to select between each type in case a target is visible to one and not another.

There is also talk of applying computer image analysis to thermal imaging that can detect anomalies in the scanner area and mark them for the operator to investigate.

The unit I’m reviewing is owned by a friend I will call Apollo, for the Greek god of light. He has worked with a wide array of technology over the years and has spent a lot of time with the electromagnetic spectrum, video, photography, and a host of other things I have trouble understanding. Much of Apollo’s time has been at a major university. In his spare time, he is a very serious gun guy who has shot most everything from an action pistol to a long range rifle. He grew up traveling the world with his scientist father and traipsed through revolutions, roadside ambushes, and the like as a child and teen. Apollo is very aware of what the world can dish out, but it doesn’t shake his strong faith as a Christian. He is a very good guy and highly knowledgeable in many areas, and I’m lucky he lets me be his friend. I wanted to explain all that so you would know I had some serious help writing this. He was kind enough to let me spend several hours picking his brain and working with his FLIR LS. Without his help, I would have been underwater at times.

In case you are wondering, they call the FLIR LS a camera, because it is a video camera. It simply sees heat rather than light. While you can connect it to a video recorder, it is more likely to be used as a monocular.

Looking through the eyepiece is initially confusing. You have to tell yourself you are seeing the world in a completely different manner. It is a monochromatic world, and some things we can easily see become invisible, like light foliage and normal lights. Other things become brilliant glowing masses, like the surface of a road. Things like cars take on different shapes. Black tires glow white from the heat made as they rolled over pavement.

What is shocking is how visible animals and particularly people are. Apollo says this unit can detect an unshielded human at 1,000 yards, even if they are in the deepest shadow on the darkest night. Based on the couple of hours I used it, I believe him. I was especially impressed with how well I could see him at 100 yards through brush. While it broke up his shape, it was patently obvious that there was something there I needed to check out.

I was quite surprised by how easy it is to see footsteps using the FLIR LS. You leave less of an imprint with thick soled shoes, and they do fade fairly quickly, but if you aren’t too far behind someone, you can probably follow them with the FLIR.

I did find the narrowness of the view makes it a little difficult to maintain situational awareness. You can, if you don’t stay sharp, lose a target. The field of view isn’t large, so you have to keep scanning or you will miss something. Scan too quickly, though, and you may go past a target.

There is a visible laser in the unit, so you can mark a target for someone without a thermal imager, but you can’t see it through the imager.

You lose night vision in the eye looking through the imager. This is a common problem, however, with all night vision gear. Most of us will bring it straight up to our master eye to view with it, but that could be a problem for a shooter, unless they also have a thermal or night vision sight. It would be better to use the non-dominant eye and save the master for the sights.

I had trouble trying to use it as I walked around. Objects that are close go out of focus. As I already mentioned, light foliage sort of disappears, so I walked into branches. I had a lot of trouble keeping both eyes open, and even if I did, the brightness of the viewfinder overwhelmed my brain, so that’s all I really saw. Overall, if I had to use night vision to negotiate a trail in the dark, I would probably feel more comfortable using a SWIR type. This may be simply a matter of my limited experience with thermal. I suspect it also has to do with the limitations of the tiny screen in the unit. On the occasions I’ve gotten to ride in a FLIR equipped helicopter, it seemed a lot easier to see. The overhead view might be a factor.

Things look more natural to me using the SWIR viewers. I think that might be because we are used to seeing things by reflected light. I get a better sense of distance and depth with SWIR than I did with thermal. That said, I can see things, like animals, far more easily with thermal; that, to me, is the most important element of this discussion.

When blended SWIR/LWIR units come down in price, they will make for a much better experience, judging by the videos I’ve seen from them.

I wish the battery pack in the unit were user replaceable. This sort of pack usually gives at least five years of service, but you could power it with an external pack, should the internal battery die and you can’t get it replaced.

I didn’t get to use it on a cold night. Apollo says the colder it is, the better it works. That agrees with what I saw in some videos using thermal in the snow. It also seems to work beautifully over water. It would be outstanding for finding a swimmer in the water.

One quirk is that it can’t see through glass. Images reflect nicely from glass, but glass blocks the wavelengths that image heat. Some think this means a sheet of glass could make a shield, but glass looks different from other objects in nature, so an alert observer might give a piece of glass in an unusual location a second look. Glass also gives and takes up heat at a different rate than most natural terrain, and if you touch it or even get close to it, it will warm rapidly, giving away your position.

FLIR Sytems makes a bewildering number of thermal imagers. Some have industrial and construction applications. Marine and aviation uses are also covered by the product line. There are several models for public safety as well as models for sportsmen. The FLIR LS Apollo chose appears to be a good blend of features for the prepper, but I’m not sure if one could be served almost as well with a lower cost model. I would rather give up some capability and at least have it than hold out for the best. They start at about $1,800, and apparently the sky is the limit when you get into the military area.

There are rifle sight versions as well as viewers, and they are quite popular with hog and predator hunters where it is legal to shoot at night. YouTube has a number of videos of this equipment in use by hunters, and it can help give you an idea of how well they work. These start at $3,500.

FLIR Systems, Inc. is a U.S. company. The unit I reviewed had stickers inside proclaiming that the key bits are made in the U.S.

My minor quibbles with the limitations of this technology do not in any way reduce my desire to own it. I always fret over anything that uses electricity or depends on advanced technology, but I think this is a game changer if you have to operate in the dark. Since I don’t control the sun, I am going to spend a lot of hours in the dark. This could save one’s life, if things were to go wrong. On the other hand, if you are up against someone who has it, you are in trouble. It would be wise to do some searches on countering thermal imagers to start getting some ideas on how to deal with it. Despite the effectiveness of this technology, you can erode its power if you have some knowledge. This site has what Apollo says is knowledgeable information on countering thermal imaging. It discusses how different materials have different levels emissivity of thermal energy, which is helpful for understanding the issues. An object that emits thermal more efficiently will look brighter than a less-efficient one, even if they are of the same temperature. This could make hiding even more complicated.

There are a lot of night vision users on this site if you want to do some further research on the devices themselves and how hunters use them in the field. – SurvivalBlog Field Gear Editor, Scot Frank Erie

Bookmark the permalink.


Leave a Reply

Your email address will not be published.
Anonymous comments are allowed, but will be moderated.
Note: Please read our discussion guidlelines before commenting.