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Trying Out Infrared

Marc Rochkind



The electromagnetic spectrum, as you recall from high-school physics (?!), ranges from gamma-rays at one end to radio waves at the other. In-between is a sliver of visible light with wavelengths of roughly 400 to 700 nanometers. Just below 400 is ultraviolet, and just above 700 is infrared.

Infrared is interesting photographically because lots of things that emit or reflect visible light also emit or reflect infrared, but differently, and because it's possible to record infrared on a photograph. The old way of doing this was to load your camera with infrared-sensitive film and put an infrared filter in front of the lens to block visible light. If your camera was an SLR, that meant you couldn't see to compose the image. Not only that, but the focus would be off, since cameras are designed to focus on visible light, and probably the exposure would be off, too.

The new way is to exploit the fact that sensors in digital cameras are already sensitive to infrared light and actually have IR-blocking filters in front of them so that infrared doesn't ruin the picture. So, all you have to do is remove the IR-blocking filter, replace it with one that blocks visible light, and you've got an IR digital camera. Since the filter is behind the mirror, you can still see through the lens just fine.

The camera won't focus correctly if that's all you do, which means you have to compensate by moving the focus slightly after the camera focuses. (Older lenses have marks for exactly this purpose.) But another camera modification can fix that problem by moving the sensor, so it's exactly the right distance from the lens.

Oh yes... one very serious disadvantage: The camera no longer works normally. All the pictures come out red, like the one at right. Another disadvantage, less serious, is that if you have the work done right it'll cost you about $450 and void the warranty on your camera. I had a Nikon D70 that was already out-of-warranty, which I wasn't using anyway, so I sent if off to MaxMax, who did the modification and sent it right back.

My modified D70 arrived last Thursday. Near as I can tell, it functions exactly as it did before: There's no difference in what I see in the viewfinder, and the focus seems to be right. Inside, though, it's very different.

I took the camera outside yesterday and shot the most boring picture of my front yard you can imagine. But look at the results below. I started to fantasize that cameras come from the factory set on "boring" with the invisible interesting picture blocked off. You just block the boring, liberate the interesting, and even your front yard starts to look pretty good.

Today, with more time, I set off for Boulder's Chautauqua Park, right up against the mountains, and then to Columbia Cemetery, a short distance away. A few results are shown at the top and below. The last two photos are in what's called "false color." Instead of converting the reddish picture to B&W, I left it in color but played around with the HSL tab in Adobe Camera Raw 4. The first interpretation is extreme; the second is more subtle.

I processed all of these IR pictures with the new Adobe Camera Raw 4.0 (available as a beta to anyone who already has Photoshop CS2); I did nothing in Photoshop. What I did in ACR I could have also done in Lightroom (also available as a beta, with no requirement to have Photoshop), since the controls and, importantly, the smart new automatic grayscale processing, appear to be identical. After the automatic conversion, I tweaked the sliders on the HSL/Grayscale tab and upped the sharpening a bit. That's all I did. (The new B&W adjustments in Photoshop CS3 are getting lots of attention, but the even more wonderful new B&W features in ACR4 seem to be largely overlooked.)

Unfortunately, some of the most dramatic IR effects are on clouds, haze (which IR can penetrate), and foliage, all of which are in short supply this winter in Boulder.

There's lots of stuff on IR digital photography on the web. Two articles that will get you started, which are mainly about modified cameras, are here and here. If you want to try IR with your unmodified digital camera, here's an article about that.

Text and photos ©2007 by Marc Rochkind. All rights reserved.

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