Infrared (IR) photography can provide some unique, very striking images. Blue skies are nearly turned black, while grass, trees, or skin can take on an eerie, ethereal glow. Having that option in your toolkit can be very tempting.
As with so much else, there’s a catch. In the film days, you needed special IR film and an IR filter (which filtered out the visible parts of the spectrum to leave you with mostly infrared light) to capture that part of the spectrum. Digital sensors, left to their own devices, will pick up the IR and UV (ultraviolet) parts of the spectrum just fine on their own. Therefore, most digital cameras have what’s called an antialiasing filter installed in front of the sensor to block out IR and UV (ultraviolet) rays that could otherwise make a mess of your photos. Over the years, these filters have gotten stronger and stronger, making it nearly impossible to attach an IR filter and get anything close to an IR image.
If you’re really serious about IR photography, your best bet is to get a secondhand camera (like a Nikon D70) that has a weak antialiasing filter, or sending your existing rig in for modification. Either of these options will run you a considerable amount of money (and the latter option, if I’m guessing correctly, is likely to make your warranty vanish like steam from a bathroom mirror). There’s another option: pick up a secondhand film body* and some IR film (Ilford makes a pseudo-IR 35mm film that’s well-reviewed and not as tempramental as the older IR stock from companies like Kodak), and snap away. The advantage to this, naturally, is that you can shoot regular 35mm to your heart’s content if you get bored with IR.
In any event, it’s a good idea to think about exactly how much IR photography you’re going to do. It’s a bit like cilantro; some people love the stuff, others can’t stand it, and its overuse gets quite tired very quickly.
The conventional wisdom about filters is that since your gear is only as strong as its weakest link, you generally don’t want to cheap out on whatever you stick on your lenses. While that’s true in a lot of cases — indeed, I’ve seen cheap UV and polarizing filters cause more issues than they were supposed to solve in the first place — this is one place where I’d suggest you go with something inexpensive if you decide to ignore my advice and try IR photography with a newer camera. Given that you’re not likely to get true IR results, all you’re going to be doing is sticking a very strong red filter on your lens (see the images that accompany this piece). Nothing wrong with that, but plunking down $100.00 or more for something that’s very easy to do with a few clicks in Photoshop or GIMP is a silly use of money that’s probably better used elsewhere.
*If you’re going to go the film route, I’d suggest getting a cheap old rangefinder. Once an IR filter is on a conventional SLR — where, remember, the viewfinder shows the view through the lens — you can’t see a darn thing. Since a rangefinder usually relies on split focus (through a finder that doesn’t rely on the view through the lens), it’s a lot easier to compose and focus.