There are 3 Main items that are very important to the overall performance of any thermal Camera.
You should ALWAYS consider these when purchasing any Thermal Camera:
- The Sensitivity of the Unit
- The Resolution of the Unit
- The Lens or Lenses that come with the unit (F Number)
Some other considerations are:
Ability to Change Lenses
A number of Thermal units have the ability to swap lenses; now this REALLY extends the usability of any Thermal Unit - Being able to match the lens to the situation allows you to access the true abilities of the units - up close and wide and far away all with one unit!
Of course you must think about the ranges and what you expect to actually see at those ranges, short 19mm lenses may be able to "detect" a human at 500m, but what will you see - a few dots?! - the lenses give you optical magnification to really see what you are looking at - its important that you take this into account when choosing a unit as most have a fixed lens that cannot be changed.
Of course then you need to think about features, layout etc - but the above are CRITICAL to the performance of any Thermal Unit