Buying your first thermal imager: A comprehensive guide

Sunday, January 8, 2017
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Buying a thermal camera is always exciting. Whether you’ve never held one before or have been using them for decades. It’s great technology which doesn't stop to amaze us at times. However, with so many devices available it can sometimes be a bit overwhelming for first-time buyers. Please read our comprehensive 'beginners guide to buying a thermal camera' to bring down your chances of disappointment.

Do I really need one?

However you look at it, thermal cameras are not cheap. And unless you’re sitting on a huge pile of cash the average Joe has to save up and weigh their options carefully. Always consider the aid of classic night vision devices as well, especially for identification purposes. And…what about a powerful flashlight with focusable beam? That might sound a bit weird coming from us, but often it’s all one needs. Let’s say you’re patrolling a 50m x 50m perimeter in the darkest conditions. Thermals might seem a good fit but can be a bit of an overkill considering startup times, resolution and a way smaller FOV than your very own pair of eyes. Pulling out a flashlight from its holster is often way quicker and more efficient. Also keep in mind the intruder who would be blinded and scared off more easily out there facing your floodlight.

What about hunting, it will definitely improve my chances right? It all depends. Try to go out on a regular clouded night and you’d be surprised what your eyes can pick up without the aid of thermal or classic night vision. There are few pitch black places out there. And are you planning to mount a thermal sight to your weapon or use a handheld monocular to scan the environment? These decisions can have a great impact on the amount of money you’ll have to save up.

Read, read, repeat

We can’t stress this enough: Try to absorb as much information on thermal imaging and its technology as possible. You don’t have to be an expert obviously, but by spending a couple hours of research on the subject you will gain lots of valuable insights and it gets you some questions answered in the process.

Finding your perfect fit

As with all purchases, deciding on your new device will be a lot easier when you know exactly what you want. We’re going to break this down into the most important parts:

  • Form factor
  • Thermal sensor
  • Optics
  • Durability
  • Battery life & type
  • Brand
  • Seller

Form factor

Start by choosing your desired form factor. Night vision thermals come in a variety of form factors which we can divide into the following categories:

  • Monoculars
    Easy to carry around and built for one-handed operation. Ideal to scan your environment quickly in a variety of conditions. Choosing this option gives you plenty of choice between various manufacturers and price ranges, from entry level to high-grade military optics. Some monoculars can be easily mounted to your weapon as well. If you’re not quite sure what you want, this is usually the category to look into.
  • Weapon sights
    For the serious hunter, law enforcement and military operations. Their build quality and optics usually exceed the monoculars. They have to operate in a wide range of conditions and be able to withstand harsh recoils from even the most fearsome guns. A lot of new innovative functionality is built into these devices which later find their ways to monoculars. Barometers, range finders and ballistic calculators are just some of the features which increase your chances of a hit.
  • Binoculars
    Usually found at border patrol, law enforcement and military operations. Comparable to the monocular in terms of functionality but with stereo vision to give you a better sense of depth which makes estimating distances easier. Please note that binoculars feature two geranium lenses and two thermal sensors increasing the price.
  • Bi-oculars
    Unlike binoculars these consist of a single lens and thermal sensor but with two eyepieces to make viewing more comfortable. While sacrificing depth of field they often make up by including high grade optics which makes them ideal for long range observation.
  • Clip-ons
    Can be placed in front of your daytime shooting sight enhancing it with thermal capabilities while keeping the reticle which you're familiar with. Some clip-ons are made for handheld operations as well giving you a wider variety of uses. If you like to easily switch between thermal and regular view this is a good option.
Thermal camera form factors
From left to right: Monocular, weapon sight, binocular, bi-ocular, clip-on

Thermal sensor

At the heart of each thermal camera you’ll find the infrared imaging sensor. It’s basically an array of micro thermometers (pixels) which senses infrared radiation. Each pixel will convert infrared heat to an electronic signal which will be processed by your units GPU/CPU and finally be shown on the integrated screen. The number of horizontal and vertical pixels on the sensor make up the ‘resolution’ of the device. Compare it to your computer monitor. Your old monitor may have a resolution of 640 x 480 and by looking at it today you will notice jagged edges and general ‘blocky’ feeling (Minecraft anyone?) . Bump this up to a 1080p display and everything looks crisp and clean. More pixels = more details, it’s as simple as that. True, optics and image processing comes into play here as well but that’s something for later.

Are you planning to use your thermal for detection (there’s something out there), recognition (it looks like a person) or identification (hey Mike!)? Lower resolutions (>160 x >120 pixels) are perfectly fine for detection but if you need to ID someone who is more than a few meters away we need to step up our game.


Traditional cameras and classic night vision devices both utilize a lens made from glass to let as much light in as possible. When you try to mount this lens to a thermal camera you simply get a blank screen. The reason for this is that lenses made from glass don’t allow thermal radiation to pass through; in fact they will reflect most of it. That’s why most thermal optics are made from Germanium (Wikipedia). Other materials commonly used in thermal lenses are Zinc Selenide (Wikipedia) and Zinc Sulphide (Wikipedia). Their characteristics allow long wave infrared (LWIR) to pass through easily.

There are some similarities between thermal and regular lenses as well:

Focal length
A longer focal length gives you a narrower FOV with more zoom (telephoto) and more details. A short focal length (say 19mm) gives you a wider FOV with fewer details and perfect when choosing detection over identification.

  • Shorter focal length = Larger FOV / less detail
  • Larger focal length = Smaller FOV / more detail

f-number / f-stop
As important as the sensor of your thermal camera is the f-number. The f-number is simply put; a ratio which determines the amount of thermal radiation passing through the lens. A lower f-number (fast lens) allows for more thermal radiation to reach the sensor and gives you more contrast and details as opposed to a higher f-number (slow lens).

Always remember that without decent optics your thermal camera won’t perform well, even if it’s equipped with the best sensor available on the market.

Manufacturing costs for thermal lenses are quite high and can often account for a large portion of your thermal imager’s final price.


Does your device need to be waterproof or submersible? They’re often thought to be the same thing but of course they are not. If you’re in doubt (since some device descriptions can be rather vague on the subject) ask the seller or manufacturer first. Are you operating it in the desert, jungle or at arctic temperatures? Get yourself familiar with IP ratings and check your devices operating- and storage temperatures just to be sure.

Battery life & type

Thermal imagers use quite a bit of power, please check the device specifications to get an estimation on battery life as well as the type of battery they need. It’s always advised to buy batteries from a well-established brand for maximum durability and battery life.

Also worth mentioning is that some devices have a built-in battery which cannot be replaced. Although this has its advantages (easy charging and no frequent trips to the store for fresh batteries) it can be cumbersome as well in some situations. If the battery is or gets faulty you will need to send it to the manufacturer for replacement and if you run out of juice in the middle of a hunting session you’re out of luck and need to recharge it at home or in your car. Newer devices however have the ability to charge via a USB connector so you can charge it easily on the go with a power bank.


Familiarize yourself with the available brands. The US, Europe, Russia and China all have respectable brands carrying high quality imagers. Some of them build their own sensors too while others only build the housing, lens and software and integrate a third-party sensor. If you’re not sure about a specific brand do some more research online or ask around in the forums. Make sure to read the product warranty information as well.


Always buy from a trusted seller! Although you can get lucky on eBay or other online marketplaces it’s generally not recommended due to the high amount of scams and lack of warranty. If you happen to live close to a store pay them a visit and try out some devices firsthand. Most stores have highly experienced staff and can give you valuable advice before making your purchase. If you’re unable to try a device first it’s recommended to give the seller a call to get a more personal touch. If you’re lucky they can even set you up with a better deal than the one you found online.

Wrap up

We didn’t dive in too deep in this article but you can see deciding on a thermal imager involves lots of variables. Familiarize yourself with the technology first, learn how to read and interpret product specifications and try to get as much information on a particular device as possible. Search for reviews online and check Youtube to see your device in action. Get in touch with people who already own the device and dare to ask questions.

Good luck with the hunt for your first thermal, enjoy the process!


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