Does a high emissivity target show apparent temperatures that are close to true temperatures?

Does a high emissivity target show apparent temperatures that are close to true temperatures?

• A. Yes
• B. No
• C. Sometimes
• D. Only at high temperatures

Answer: (A)

High emissivity surfaces radiate infrared energy very efficiently, behaving like near-blackbodies. When a camera detects IR energy, it translates that radiance into a temperature based on an assumed emissivity value. If the target truly has high emissivity and the camera is set to that emissivity (and conditions like distance, atmosphere, and reflections are controlled), most of what the camera measures is emitted energy from the surface, not reflected ambient radiation. That makes the apparent temperature very close to the actual surface temperature. If emissivity is not matched, or reflections and other factors dominate, the reading can be off even for high-emissivity targets.

High emissivity surfaces radiate infrared energy very efficiently, behaving like near-blackbodies. When a camera detects IR energy, it translates that radiance into a temperature based on an assumed emissivity value. If the target truly has high emissivity and the camera is set to that emissivity (and conditions like distance, atmosphere, and reflections are controlled), most of what the camera measures is emitted energy from the surface, not reflected ambient radiation. That makes the apparent temperature very close to the actual surface temperature. If emissivity is not matched, or reflections and other factors dominate, the reading can be off even for high-emissivity targets.