ok well how is the camera accessing the part inside a container, inside a thermal chamber and why is a camera being used to measure temp and not a temp probe? If it is inside an oven and the question is why would one material in the oven not be the same temperature as other materials in the oven the conductivity of the materials is a logical answer especially since the material in question is a metal housing. Yes the reflection of light will influence measurements of light but there is no mention of light being reflected by the user I am assuming is familiar with the instrument they have chosen. Granted matter is limited but it surely within the realm of possibility that the metal housing is acting as heat sink. This is even more possible when the notion of moving air is added to the equation. Air moving over metal... what is the housing protecting the part from? The conditions should not be the same inside the housing as outside the housing because it would longer be a housing but just another part being heated returning me to my original point that the amount of energy required to raise the temp of the material will vary based upon the properties of the material. It just so happens that in this case known properties of the known materials suggest heat can and should be lost.