What’s The Difference between Thermal Imaging and Night Vision?



Thermal Imaging Cameras


FLIRs make pictures from heat, not visible light. Heat (also called infrared, or thermal, energy) and light are both parts of the electromagnetic spectrum, but a camera that can detect visible light won’t see thermal energy, and vice versa.

Thermal cameras detect more than just heat though; they detect tiny differences in heat – as small as 0.01°C – and display them as shades of grey or with different colors. This can be a tricky idea to get across, and many people just don’t understand the concept, so we’ll spend a little time explaining it.

 thermal bats




While all this can seem rather complex, the reality is that modern thermal cameras are extremely easy to use. Their imagery is clear and easy to understand, requiring no training or interpretation. If you can watch TV, you can use a FLIR thermal camera. 

Night Vision Devices


night vision view


NVG and other lowlight cameras are not very useful during twilight hours, when there is too much light for them to work effectively, but not enough light for you to see with the naked eye. Thermal cameras aren’t affected by visible light, so they can give you clear pictures even when you are looking into the setting sun. In fact, you can aim a spotlight at a FLIR and still get a perfect picture.

Infrared Illuminated (I2) Cameras

I2 cameras try to generate their own reflected light by projecting a beam of near-infrared energy that their imager can see when it bounces off an object. This works to a point, but I2 cameras still rely on reflected light to make an image, so they have the same limitations as any other night vision camera that depends on reflected light energy – short range, and poor contrast. 


All of these visible light cameras – daylight cameras, NVG cameras, and I2 cameras – work by detecting reflected light energy. But the amount of reflected light they receive is not the only factor that determines whether or not you’ll be able to see with these cameras: image contrast matters, too.

If you’re looking at something with lots of contrast compared to its surroundings, you’ll have a better chance of seeing it with a visible light camera. If it doesn’t have good contrast, you won’t see it well, no matter how bright the sun is shining. A white object seen against a dark background has lots of contrast. A darker object, however, will be hard for these cameras to see against a dark background. This is called having poor contrast. At night, when the lack of visible light naturally decreases image contrast, visible light camera performance suffers even more.

Thermal imagers don’t have any of these shortcomings. First, they have nothing to do with reflected light energy: they see heat. Everything you see in normal daily life has a heat signature. This is why you have a much better chance of seeing something at night with a thermal imager than you do with visible light camera, even a night vision camera.

In fact, many of the objects you could be looking for, like people, generate their own contrast because they generate their own heat. Thermal imagers can see them well because they don’t just make pictures from heat; they make pictures from the minute differences in heat between objects.

Night vision devices have the same drawbacks that daylight and lowlight TV cameras do: they need enough light, and enough contrast to create usable images. Thermal imagers, on the other hand, see clearly day and night, while creating their own contrast. Without a doubt, thermal cameras are the best 24-hour imaging option.

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