Emissivity is the relative ability or ‘willingness’ of an object to emit energy in the form of infrared radiation. It is required to mathematically calculate surface temperature.
Since emissivity varies widely between materials, surface structures, geometries and angles, it must be adjusted in the camera to get an accurate surface temperature reading. Particular care needs to be used when measuring low emissivity (highly reflective) materials like metals.
Many entry level infrared cameras do not offer the ability to adjust emissivity. These models should be avoided when doing quantitative analysis or when accurate surface temperatures are required.
Emissivity is one of the most important parameters involved in accurately calculating the surface temperature of an object. Unfortunately, it’s also perhaps the least understood, especially by those new to thermography. If you are new to thermography, ensure that you take the time to learn about emissivity and understand how to accurately calculate it (without relying on general emissivity tables - the values for a given material vary widely with the type of surface, geometry, angle and more) otherwise you cannot be sure that you are reporting surface temperature correctly.
Emissivity adjustment on the Fluke Ti32 using the emissivity table
Emissivity adjustment on the FLIR i60 using a measured emissivity of 0.95