Does the image from an infrared camera always represent exact variations in temperature?

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

Answer: (B)

Infrared images show how much infrared energy a surface is emitting, which correlates with temperature but is not a precise temperature readout for every pixel. The main issue is emissivity—the intrinsic ability of a material to emit infrared energy—which varies widely between materials and conditions. If emissivity isn’t known and set correctly in the camera, two surfaces at the same actual temperature can appear at different colors, and the same surface can read differently under different circumstances. Reflected ambient radiation, distance to the target, and atmospheric effects can also skew readings. Because of these factors, the image is best used to spot relative hot and cold areas and to identify anomalies, rather than to trust exact temperature values unless you calibrate for emissivity and use proper references.