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

• A. Yes
• B. No
• C. Sometimes
• D. Only in vacuum

Answer: (B)

Emissivity tells us how much of what the camera detects from a surface is actually emitted by that surface versus reflected from the surroundings. An infrared camera typically assumes a high emissivity (often near 1). When a target has low emissivity, a larger portion of the detected signal comes from reflected ambient radiation rather than the target’s own emission.

Because of that reflection, the reading tends to be pulled toward the temperature of the surrounding environment rather than the true surface temperature. Unless you correct for emissivity or the surroundings happen to be at the same temperature as the surface, the apparent temperature will not closely match the true temperature. In practice, that means a low-emissivity target generally does not show apparent temperatures close to the true temperatures.