Emissivity is the fraction of energy radiated by a material compared to the energy radiated by a black body (ideal object that absorbs all incident electromagnetic radiation without reflecting it) that is at the same temperature.
In the case of the human body the emissivity is 0.97 - 0.98, so the handheld thermographic cameras will have to be configured with these values.
For common material emissivity values, we invite you to consult the following table.
Wood 0.85
Water 0.96
Brick 0.75
Stainless Steel 0.14
Tape 0.96
Aluminium Plate 0.09
Copper Plate 0.06
Black Aluminum 0.95
Human Skin 0.98
Asphalt 0.96
PVC 0.93
Paper Black 0.86
Polycarbonate 0.80
Concrete 0.97
Copper Oxide 0.78
Cast iron 0.81
Oxide 0.80
Gypsum 0.75
Paint 0.90
Rubber 0.95
Earth 0.93