More stuff about thermal imaging.
Looking at the sensitivity spectrum for a FLIR thermal camera much of the CO2 and H2O emission spectra are included but it is not a black body spectrum as the camera expects.
So does this mean that CO2 and water vapour should be less visible to the camera?
For the camera this is important since taking a photo through air which is emitting photons visible to its sensor would make its use limited – you would see the air not the object behind the air.
So a simple test using water vapour was done to see if this was the case
Some videos of a hot plate with 2 wells filled with water, The water is boiling but no hot vapour visible (vapour bubbles show approximately the expected temperature but the only vapour visible is less than 40°C.
If you now place a sheet of paper in the vapour the actual temperature of the vapour as it hits the paper can be seen (greater than 70°C)
|Steam shows up at 28C|
|Shows paper being heated to 75.5C by steam invisible in gap between boiling water amd paper.|
|Heated plate showing 2 wells with boiling water|
These videos show differen views of the hotplate - steam - paper system.
Steam visible + paper
Top view of plate, boiling water and paper
side view of plate boiling water and paper
Above videos seem to have problems so a youtube version:
Conclusion: H2O vapour behaves as expected - despite the temperature being near boiling (100C) it does not appear so to the camera.