In reality, a thermal imager measures , not temperature. It then uses complex algorithms to convert that radiation into a temperature reading. Any mistake in the variables you feed the camera—or environmental interference—leads to errors.
There is a common misconception that an infrared (IR) camera simply takes a picture of heat. If that were true, thermography would be the easiest skill in the world to master. Point, shoot, and find the hot spot. infrared thermography errors and uncertainties pdf
Infrared thermography is a science, not a magic trick. By understanding the difference between radiated energy and true temperature—and by quantifying your uncertainty—you transform from a "button pusher" into a diagnostician. In reality, a thermal imager measures , not temperature