Both technologies help you see in low light, but they work on different principles and suit different jobs.
How night vision works
Night vision (image intensification) amplifies tiny amounts of visible and near-infrared light, such as starlight or moonlight, and shows a brightened picture. It needs at least some ambient light, or an infrared illuminator, to work.
How thermal imaging works
Thermal imaging detects heat emitted by objects, so it needs no light at all. Warm things stand out from cooler backgrounds whether it is pitch black or broad daylight. For the technical background, see how thermal cameras work.
Side by side
- Total darkness: thermal works. Night vision needs some light or an illuminator.
- Spotting warm targets in cover: thermal is usually better because heat contrasts with foliage and terrain. Heavy cover can still hide a target.
- Fog, haze and smoke: thermal often copes better than visible light, though dense conditions reduce range for both.
- Seeing detail and faces: night vision shows more familiar visual detail. Thermal shows heat patterns, which is less like a photograph.
- Seeing through glass: neither is dependable. Thermal cannot see through ordinary glass at all.
- Daytime use: thermal works in daylight. Night vision is normally for low light only.
Which should you choose?
If you want to find warm things, such as wildlife, people or hot equipment, thermal is usually the better fit. If you need to read signs, identify features and see ordinary scenes in low light, night vision may suit better. Many people use thermal for finding and a conventional optic for confirming.
Explore thermal monoculars and read how to choose one.