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In-Camera Digital Infrared - 5/11/09

Make actual infrared photos with your D-SLR

This Article Features Photo Zoom

Often, film effects recreated digitally after a picture is made—by post-processing in the computer alone. But there’s an old-school film effect that requires some special in-camera consideration even when shooting digital—infrared photography.

Digital camera sensors see well beyond the visible light spectrum that’s needed for normal photographic capture. That’s why digital cameras include an infrared filter over the sensor—to eliminate that extra IR information that does nothing but interfere with normal digital capture and would actually hamper traditionally sharp photos.

But what about when you want to get some infrared information in your photos? The key to making a digital infrared image is to filter out all the light that you don’t want, and let in only the light you do. That means using an infrared filter for specifically that purpose. Some photographers have been known to manipulate their cameras to remove the internal IR filter that doesn’t allow infrared light waves to pass and then add an infrared filter to the lens that only allows infrared light to pass. This is by far the best approach to digital infrared since it maximizes the camera’s ability to see infrared and infrared only.

But just because it’s the best method doesn’t mean it’s the only one. After all, what if you don’t want to dedicate a camera to solely infrared capture? In that case you’d better leave the internal IR filter alone. Internal IR sensor filters aren’t perfect; that sensitivity to even minor amounts of infrared light, combined with an infrared-transmission filter on the front of the lens, can make for digital infrared photos without fakery and without permanently modifying a camera.

The average film photographer shooting infrared photos used infrared film and a filter on the lens—often the deep red #25 that was also useful in traditional black & white. The deep red of the #25 filter only allowed those red—and infrared—lightwaves to pass.

An even better filter for infrared is an even darker red—the almost black #87 filter and its variants. Trouble is, most photographers don’t have this filter lying around because it served no other purpose than to eliminate all but the infrared light in normal film photography. If you’re going out to buy a filter for infrared digital, this is the way to go. But if you’re working with the tools you already have around, grab that plain old #25 red and put it to good use.

Once you’ve got the IR filter on your lens, you’ll notice that focusing becomes a chore. True infrared light actually focuses at a different point than the visible light we’re used to. That’s why many film lenses actually have a second focusing mark specifically for infrared. Digital camera autofocus may be fooled by the filter, but only in as much as it will have a hard time seeing through the darkened glass. Consider not only manual focusing, but doing it with your camera on a tripod and a trial and error approach to focusing. Thankfully, the digital LCD can show you how accurately you’re focusing—even if you can’t see through the viewfinder.

With a red filter on your camera’s lens, your photos obviously turn red. Not just a little red, but really, really red. This is actually a good thing. If you were to simply desaturate that image you’d be well on your way to an infrared image. A particular grayscale conversion combined with some levels adjustments, however, is even better.

The best way to convert a really red color image into an infrared black & white photo is to isolate channels in Photoshop. This can be done with the Channel Mixer, much as you would for a regular grayscale conversion, or by simply isolating and eliminating channels in the RGB channel palette.

With the channels palette open, click on the red channel to isolate it. Then in the Image>Mode menu, convert the image to grayscale. The program will only use the red channel for this grayscale conversion, and you’re likely to see a great image with good contrast, a darkened sky and white foliage—much as you would with a “real” infrared image. To make the effect even more pronounced, adjust curves and contrast as necessary.

The only thing really missing is the gauzy, otherworldly effect that’s so often a part of interesting infrared imagery. You can recreate that effect in the computer as well. Simply duplicate the faux infrared image onto a new layer, and run a Gaussian blur filter—just enough to create a general glow but without eliminating all image detail. Then in the layers palette, adjust the layer mode to Lighten. This will allow the darker tones of the original image to show through, leaving only the blurred layer to create the gauzy halo around the highlights—a recreation of the Wood Effect of blurred highlights common in infrared images.

The natural world makes for an ideal infrared subject, so that’s where most photographers seem to have the best luck. Perhaps the best thing about infrared imaging is that it can truly make mundane subjects absolutely interesting. Take a tree, for example: In color, it’s boring. In black & white, it’s somewhat interesting. But in infrared, it can be amazing!

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