You can enjoy this post about two little science experiments with the IR digital camera and the InGaAs camera we use for art examination. These experiments have nothing to do with art documentation but, I know, some of you are scientists and would enjoy them.
Blackbody Radiation and Thermal Infrared
A thermal camera is actually pretty affordable nowadays, but we can still see thermal infrared with the digital modified camera for infrared photography or even better with the InGaAs camera for Infrared Reflectography.
When I was teaching thermographic imaging I used to introduce the class with the concept of black body radiation. Any object, with a temperature over the absolute zero (Kelvin temperature scale), will emit radiation. When the temperature of the object is low the radiation would be in the infrared region, when the temperature rises to thousands of degree Celsius this blackbody radiation becomes visible light (for example, melting iron). When the temperature rises more into, let’s say, the temperature of the Sun, then the radiation goes also into the Ultraviolet range. The University of Colorado at Boulder made a nice applet, very useful to explain this concept ][1].
I tested my little hotplate. When the hotplate is switched on its temperature can go up to about 800 degree Celsius. As shown by the applet, the blackbody radiation would have a tail below 1100 nm, the digital camera actual infrared limit. The digital camera can detect this thermal radiation, as well as the InGaAs camera (with cut off filter 1500 nm).
University of Colorado at Boulder Blackbody radiation applet [1]. An object at 800 degree Celsius emits radiation in the close infrared, below 1100 nm. The hotplate is switched on. A digital camera can see the thermal infrared, as well as the InGaAs camera with a, cut off filter at 1500 nm.
Water, infrared radiation molecular absorption
Water absorbs infrared radiation over about 1000 nm [2].
Water absorbs infrared light over 1000 nm. In the digital infrared range below 1100 nm water, it’s still transparent but becomes opaque when seen with the InGaAs camera with a 1500 nm filter on. My business card is inside the glass.
