We call a thermography device a “camera” but it is does not actually “see“ the image like a camera we are familiar with; it is detecting temperature only. The variation in temperature actually makes the image look familiar. The higher the resolution the greater the detail so that we might even recognize the person in the thermal image.
A high quality thermal device has the ability to convert the data into temperature within the device (not in the computer), which is the most accurate temperature. It is customary to use Celsius for medical imaging and interpretation. The most significant indication of a thermal abnormality is a side-to- side temperature difference, as the person is their own control; meaning one person is not compared to another but the comparison is made between the left and right sides of the body.