FLIR Navigator II Operator's Manual page 22

2) At a given temperature, the amount of thermal energy radiated by an object
depends on its emissivity. Emissivity is the measure of an object's efficiency at
radiating thermal energy. For example, shiny metals are poor emitters. Instead
of radiating their own thermal energy, they tend to reflect radiation from
their surroundings.
Infrared, from theory to practical application
Infrared imagers operate by detecting the relative intensities of thermal energy
radiated from the surfaces of objects, and displaying these intensities in black
and white video as shades of gray.
an object is very hot, it may not display well if there is little or no temperature
contrast between the object and its surroundings.
ermal imagers primarily detect thermal energy radiated from an object's
surface; thermal imagers can't "see through" much of anything, except some
plastics and nylon materials.
As you look at the thermal images created with your Navigator II, you will
see multiple sources of thermal energy in addition to your main object of
interest. When looking at a scene with a large number of heat sources, it can
get confusing trying to sort it all out. Kirchhoff's Law is an easy way to account
for the different sources of thermal radiation you see in your images. Kirchhoff
says that all of the thermal radiation in an image has been Emitted (given off
by an object), Transmitted (passed through an object), or Reflected (bounced
off an object).
Most of the strong energy sources you will see in a given scene are from
"emitted" energy.
emitters of thermal energy include people and boat engines.
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ey do not show a "heat picture." Even if
at is, they are giving off heat energy. Examples of strong
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