Infra-red (IR) is a color spectrum beyond the red end of the rainbow. Our eyes can’t see it. But our cameras can, provided we’re out to capture it. And when we do, the results can be stunning, yet difficult at best to achieve.
Yet, more than thirty years ago, long before the advent of digital media, it was even more of a hassle: special film handling, black-and-white processing, and inability to evaluate results (or adjust settings) until the whole roll of film was exposed and the pictures were printed. Now, this has changed. Due to the arrival of digital photography, we can afford to take infrared pictures whenever we please, as many as we wish, mix them with “normal” ones, and see results on the spot, tweaking our settings to our hearts’ desires.
But a lot depends of course, on how your camera sensor array reacts to the infrared — as well as d on the filter(s) you are using, at the far red end of the visible spectrum.
IR photography has now become a lot more enjoyable and can be a lot of fun because green trees and plants reflect a lot of the IR spectrum so they appear quite bright in an IR image. Likewise since the blue sky has almost no IR, the sky almost always looks black with clouds standing out brilliantly within the IR spectrum. Haze and fog can scatter the blue light, having little effect on infrared, so the IR images actually can cut through much haze and fog leaving a beautiful image.
There are different types of red infrared in the spectrum with our equipment capturing the “near” IR spectrum—the closest spectrum to red. What we photograph in the near IR is not heat generated. Heat is a longer type IR in the spectrum and much further away from the red we capture, and cannot be photographed with the ordinary equipment and film we use.
Scientists describe colors with wavelengths. Blue is from 400 – 500 nm (nanometers), green is from 500 – 600 nm and red is from 600-700 nm.
IR starts at 700 nm in photography and extends to about 1,000 nm, when 1,000 nm is referred to as a micron. Longer wavelength IR is used in systems to see heat work between 1 – 10 microns or 1,000 to 10,000 nm.
THE I.R. FILTER
These can be purchased from any dependable mail-order supplier, such as B&H Photo.
Various filters may differ in the visible light cut-off point (see the table below). The Wratten #89B (available as Hoya R72), with the light transmission falling down to 50% at 720 nanometers, seems to be most popular and gives the greatest chance of success. The darker #87 or #87C may or may not work, depending on the camera, while the almost-IR #70, while allowing for shorter exposure times, does not provide the eerie Woods effect on greens.
You also need a way to attach the filter to your lens. This is easy with SLR and digital-finder models, but digital compacts may pose a problem. With a very few (like the Olympus C-5060WZ) you can do it directly, as the lens is threaded; with most others you will need a lens adapter tube, like the 41-43 mm CLA-1 attachment for the Olympus C-5050Z (plus a step-up ring).