"Wood was credited with 'opening up two new worlds; the worlds at each end of the spectrum'..."
Professor Robin Williams, RMIT University, Australia
Traditional photography relies upon the interaction of visible light with film or plates to produce an image. As visible light makes up only a small portion of the electromagnetic spectrum, it follows that images could also be produced by infrared (IR) or ultraviolet (UV) light, which flank the visible in the spectrum.
The first intentionally produced infrared images were taken by Professor Robert W. Wood. (1868-1955) and displayed in 1910. Wood used a filter over the camera lens to remove all but the infrared light and a film that was sensitive to IR. The technique was used initially for landscapes, because of its long exposure times. Chlorophyll reflects large guantities of infrared light, making foliage appear bright white, while clear blue sky appears almost black.
IR photography is used in aerial surveys and military reconnaissance as it enables the depth of water and the presence of underwater obstacles to be seen. It is used in forest surveys to distinguish coniferous and deciduous trees, while botanists can use it to observe changes in pigmentation and cellular structure as plant diseases progress. Astrophysicists use it for observing distant galaxies and discovering new stars. IR and UV photography is also used to examine damaged documents by comparing inks.
