Emissivity or in shorthand ε or e is a percentage of how much heat an item can radiate as compared to a black body (1.0). A low value indicates low emissivity while a higher value indicates a higher emissivity – the higher the number the more accurate a temperature reading you can get with an infrared camera. There are 5 main factors that effect an object or materials emissivity:
- The material itself (Black hole box – near perfect emissivity 1, human face .98, black electrical tape .95, copper .02 to .6, etc…)
- The surface (Rough, Polished, etc…)
- One’s angle of view (while you should not be looking directly at the item, you should be as straight onto it as possible – i.e. standing 5° off to the side)
- The temperature (while rare, the hotter metal gets, their emissivity can increase to the point of showing up in the visible spectrum)
- The wave length (Mid or Long – see FAQ’s for chart)