For the human eye, the lowest visible wavelengths are red light measuring about 700 nanometers. Below that, infrared radiation runs from about 750nm down to 1mm. In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. When photographed in the infrared part of the spectrum, leaves and grass glow with energy, as if the entire natural world is lined with fiber optics.
One of the attributes of infrared photography is that sky appears very dark, while clouds glow with brightness. The darkness of the sky is due to infrared penetration of atmospheric haze, caused by a reduction in Rayleigh and Mie scattering when compared with visual light. This type of scattering is the distribution of light and electro magnetic radiation in the atmosphere. When captured with infrared photography, the dark skies often lend images an extraterrestrial feel.
Infrared photography ... actually science has given us a glimpse of our world that has been hidden beneath an invisibility cloak ...blue trees ..thats just crazy, God must have "artist" printed on his resume somewhere :)