Infrared Photography - 1/2

Infrared Photography

Due to the arrival of digital photography, we can take infrared pictures whenever we please, mixing them with “normal” ones, and see results on the spot, tweaking the settings to our hearts’ desires…All depends, of course, on how your camera sensor array reacts to the infrared ��" and, depending on the filter you are using, to the far red end of the visible spectrum.

At the first glance, a monochrome picture taken in infrared may look similar to just another black and white photograph. And then you start seeing differences: objects which are bright in visible light (like sky) look dark here, while some of those which are “normally” dark (green foliage) acquire a bright glow. An unusual and eerie feeling.

The most dramatic difference between the visible and infrared spectrum is in case of foliage: it does, indeed, become very bright in infrared. Photographs in infrared show quite unusual tonality, different than that to which we are used, and this may make them esthetically pleasing, at least in many cases. Which, of course, is a matter of taste.

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. Wavelengths used for photography range from about 700 nm to about 900 nm. Usually an “infrared filter” is used; this lets infrared (IR) light pass through to the camera , but blocks all or most of the visible light spectrum (the filter thus looks black or deep red).

When these filters are used together with infrared-sensitive film or sensors, very interesting “in-camera effects” can be obtained; false-color or black-and-white images with a dreamlike or sometimes lurid appearance known as the “Wood Effect,” an effect mainly caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow . There is a small contribution from chlorophyll fluorescence, but this is marginal and is not the real cause of the brightness seen in infrared photographs. The effect is named after the infrared photography pioneer Robert W. Wood, and not after the material wood, which does not strongly reflect infrared.