Should You Convert an Old Camera to Infrared or Buy a Filter?

If you've wanted to try infrared, you have two choices: screw a filter onto the camera you already own, or send a body off to be permanently converted. The two routes differ a lot in cost, commitment, and how much patience each shot demands.

Ben Harvey tests both methods side by side on the same sunlit building, Lancing College, in the same morning light. His converted body is an old Canon EOS 550D with a 720 nm conversion and a Canon EF-S 10-18mm f/4.5-5.6 IS STM. The filter setup is an unmodified Canon EOS 5D Mark III with a Canon EF 16-35mm f/4L IS USM and a borrowed Kenko 720 nm infrared filter. At f/8, ISO 200, and 1/60 s, settings Harvey says are fine for handheld shooting, the converted camera produces a well-exposed frame with a histogram he calls "bang on." Getting the same composition through the filter took a 2-minute exposure.

The filter route also asks for more setup before the first real frame. Point a regular camera through a 720 nm filter and everything comes out deep red, so Harvey sets a custom white balance by photographing sunlit grass through the filter. You only do this once, and the camera remembers it. If you plan to convert everything to black and white in Lightroom anyway, you can skip it. The filter cuts somewhere between 10 and 12 stops depending on the filter and the light, so Harvey works out the exposure with a long exposure calculator, misses on the first try, and adjusts. You can't see through the filter well enough to compose or focus, so every change of framing means removing it, recomposing, refocusing, and screwing it back on.

The 720 nm conversion Harvey uses, which he calls the sweet spot, sits in the middle of a range. Conversion services offer filters at roughly 590 nm and 665 nm, which let more visible light through and give stronger false color, and 850 nm or higher, which produces deep, nearly pure black and white with little color left to work with. There are also full spectrum conversions, which swap the infrared-blocking filter for clear glass. With one of those, you put the infrared filter on the lens instead of behind it, swap between wavelengths at will, and add a hot mirror filter on the lens when you want normal color photos. Handheld shutter speeds stay available because the sensor isn't fighting the filter. The camera type matters too. Mirrorless bodies focus off the sensor itself, so they sidestep the infrared focus shift that can leave converted DSLRs slightly soft unless the autofocus is calibrated for it. That makes older mirrorless bodies an appealing candidate for conversion, especially if one is already sitting in a drawer.

Those long exposures happen because most cameras have a filter in front of the sensor whose job is to block infrared. Put an infrared-only filter on the lens and you're asking the camera to record the very light its own sensor stack is built to reject, so only a trickle gets through over a long exposure. A conversion removes that blocking filter and replaces it with one that passes the chosen infrared wavelength. Harvey shows how firm that limit is: even at f/4, 1/50 s, and maximum ISO, the filtered 5D Mark III returns a black frame. The colors on the two camera backs also look quite different, even though both setups use 720 nm filtering. Harvey says it could be the specific filter or the way the 5D Mark III handles infrared, and he suggests looking up what results other people have gotten using infrared filters with your camera model. Reviewing the files later in Lightroom, he found two more problems with the filter images. One is a heavy vignette that shows up even when he zooms in from 16mm and avoids wide apertures, though with only one filter tested, he doesn't claim every filter will do it. The other is foliage that won't glow the way it does from the converted camera, with one tree staying dark green. He heads out again to the Royal Pavilion in Brighton to try to track down the vignetting.

Harvey puts a conversion at about £200 to £300 (roughly $250 to $400), and it's permanent: that body will never take a normal photograph again. Buying a used camera that's already been converted is another option. A 720 nm filter like the Kenko or the Hoya R72, which Harvey has also used, costs much less: he puts the Kenko at around £100 (about $130), with larger filter sizes costing more. If you shoot with more than one lens, you'll likely buy the filter for your biggest thread and carry step-up rings for the rest, and leaving those rings at home means the filter won't fit the other lens. Harvey also points out that a converted camera can still shoot long exposures with ND filters, while the filter route forces them on you, blurring moving leaves and cutting how many frames you get when each one takes 1 or 2 minutes.

His side-by-side comparison images are in the video above.