How face masks and glasses change your thermoscan

This was an experiment back in May, when COVID-19 was new and everyone rushed for thermal scans hoping they would reveal infections. Because I had it, I set up a cheap DANIYO HY-18 handheld thermal cam, and an Intel RealSense D435 cam to tinker with images, ultimately I wanted to locate the forehead.

Before I went off into detecting my own forehead from a 3D image, I assessed system accuracy. Primary sources are things that you may wear in front of your face, like face masks, or frames.

no face cover
metal frame and face mask
Comparison of face surface temperatures

The results are off by around 0.75 deg C. This, of course, heavily depends on ambient temperature, this experiment took place on 2020-05-24, which had temperatures around 20 deg C, which would be a typical office or indoor setting.