Infrared filters

Infrared photography has become very popular, especially since it’s been discovered that digital image sensors are very sensitive to what’s called the near-infrared spectrum. This is light that’s just outside of visible red light, where nothing that’s illuminated by thermal radiation can be seen. Infrared filters are very dark, and make the world appear as an icy, almost ghostly stark landscape, like something out of a science fiction movie.

Most modern dSLRs, including Canon, have infrared filters in front of their image sensors; some of these filters are stronger than others. There are a couple of ways to shoot an IR image. The first is to use an infrared filter; these are very dark and block most of the visible light in a scene, so you have to take very, very long exposures — and your camera’s IR filter still may end up blocking lots of the IR light, so you will have to test your particular camera to see if you can achieve the results you want.

If you’re really serious about producing IR images, the second way is to have your camera’s image sensor professionally altered to remove the low-pass filter that normally protects it from infrared light. This is an expensive process, and most photographers use an older backup camera for this purpose because not only does it physically alter the camera permanently, it invalidates the warranty. LifePixel (www.LifePixel.com) is one such company that provides this service.

I suggest you experiment with an infrared filter first and see what your results are like before paying to have your camera altered. Using an infrared filter requires you to adjust your f-stop settings by several stops — and to have a much longer exposure. You also should use a tripod for a shot, and run the lowest ISO possible to avoid digital noise in your photo. You’ll also want to pay attention to your depth of field, which will change because infrared light tends to diffract more than other types, meaning an IR shot will end up having a shallower depth of field, and you’ll probably want to try a deeper depth-of-field setting first.

Category: Filters

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