The visual aids have now confused you?
Here, try this ----http://webphysics.iupui.edu/webscience/physics_archive/colorandtemperature.html
ALUMINA!?!?! WHAT? You've got to be kidding, no wait, the Rossi frauds have got to be LYING. Again.
What a bad joke.
Knowing the value of ε is of prime importance, both for the calculation of power emitted, and for reading temperatures with an IR camera, an instrument which does not measure the relevant parameter directly, but deduces it by means of a formula having several variables which must be supplied. Every thermal camera contains a detector where sensitive components generate an electric signal proportional to the IR radiation received. This signal is then amplified and processed by the device’s electronics, and converted into an output signal proportional to the temperature of the object. This proportionality is expressed by an algorithm dependent on several parameters, such as the internal temperature of the detector (read directly by the camera sensors), ambient temperature, and the emissivity of the radiant body. The user sets the last two parameters before acquiring the data, but they may be also modified in the course of the analysis, because the camera software is capable of re-elaborating stored results and re-adapting them to new settings. For an in-depth description on how the cameras used by us work, see [2].