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Thermal imaging
A thermal imaging device detects infrared radiation (heat) and converts temperature differences into a visible image. It works in complete darkness without any light source and is used for hunting, wildlife observation, and security purposes.
What is thermal imaging and how does it work?
Unlike a night vision device, which amplifies residual light, a thermal imager works with heat radiation. Every object above absolute zero emits infrared radiation. The thermal imager captures this radiation and converts it into an image.
Warmer objects (game, people) appear more prominently than the cooler background. Thermal imaging works in total darkness and can see through fog, smoke, or light vegetation.
Key thermal imaging parameters
NETD (thermal sensitivity) measures the sensor's ability to distinguish small temperature differences. It is expressed in milliKelvins (mK). A lower number means a more sensitive sensor:
- Below 25 mK – sufficient for most hunting situations
- Below 20 mK – for demanding conditions (fog, rain)
- Below 18 mK – professional use
Sensor resolution indicates the pixel count and affects image detail:
| Resolution | Class | Use |
|---|---|---|
| 256×192 px | Entry-level | Short range |
| 384×288 px | Mid-range | General purpose |
| 640×512 px | High-end | Professional |
| 1280×1024 px | Premium | Extreme range |
Lens size determines the field of view and detection range. Smaller lenses (15–25 mm) offer a wide view for terrain scanning. Larger lenses (35–75 mm) provide a narrower field of view but longer range for target identification.
Thermal imaging vs. night vision
| Parameter | Thermal imaging | Night vision |
|---|---|---|
| Principle | Detects heat | Amplifies light |
| Needs light | No | Yes (or IR illuminator) |
| Works in fog | Yes | No |
| Image quality | Outlines/silhouettes | Detailed (fur, antlers) |
| Detection range | Up to ~4,400 yards | Up to ~550 yards |
| Price | From ~$1,600 | From ~$550 |
For detecting game, thermal imaging is the better option. For identification and precise shooting, a night vision riflescope is more suitable. Experienced hunters combine both technologies.
Types of thermal devices and display modes
- Monocular – handheld device for observation and detection
- Riflescope – weapon-mounted sight for direct aiming
- Clip-on – attachment placed in front of a daytime riflescope
- Binocular – stereoscopic view for extended observation
Thermal imagers offer several display modes. White Hot shows warmer objects as bright and cooler objects as dark. Black Hot works in reverse. Rainbow or Iron palettes use a color scale from blue (cold) to red (warm).
White Hot is the most common choice for hunting because game stands out clearly against a dark background. Black Hot can work better when scanning the sky or snow.
Choosing the right thermal imager
Start with sensor resolution and NETD when comparing models. A 384×288 sensor with NETD below 25 mK covers most hunting needs. Choose a lens size based on your typical engagement distance – a 25 mm lens for scanning and a 50 mm lens for identification at longer range.
Related terms: night vision device, NETD, IR illuminator, detection range