# Why do thermal cameras work at infrared radiation and not at visible one?

From the Wien's law I have computed the Spectral Irradiance of a black body at 1000°C.

From different thermal cameras manufacturers web sites, a lot of Thermal Cameras work in the range 6-14 $$\mu m$$. These cameras are able to measure usually from 200 - 1400 °C.

From the following plot the maximum of the radiation is in the rage 2-3 $$\mu m$$ (in the visible band) not at 6-14 $$\mu m$$. So my question is:

Why do thermal cameras work at infrared radiation and not at visible one?

I try to plot the Wien's law for black body at 200°C but the maximum is around 6 $$\mu m$$ not at $$\frac{6+14}{2}=10$$.

• A thermal camera measuring 200 to 1400C is a pretty specialized product, A range of about -20 to 200C is more common, and more generally useful. – alephzero Sep 26 at 8:25
• 2-3 micron is not in the visible band. Visible light is more in the range of 400-800nm. – Holzner Sep 26 at 10:07