Quote Originally Posted by walter23 View Post
You're not really seeing the thermal IR part of the spectrum in your kodak HIE images. Thermal infrared involves much longer wavelengths (far IR) that this film simply isn't sensitive to. I think HIE drops off in sensitivity somewhere in the mid 900nm range, which is in the near-IR range. In the grand scheme of EM radiation it's practically visible light.
The human body heat shows up around the 10 to 15 micron range [10,000nm to 15,000nm] well beyond the range of IR film.