Camera Hack: Capture Invisible Light with Your Sigma SD14

With its easy to remove IR cutoff filter, this new digital SLR can be quickly and easily transformed into an infrared capture device.



One of the easiest and coolest camera hacks we've seen lately is possible with the just-released Sigma SD14. And best of all, it doesn't involve specialized tools, major camera dissection, or any potential warranty voiding actions.

By simply removing the infrared (IR) cutoff filter from this digital SLR, the camera gains the ability to capture IR plus visible spectrum images. And with the addition of an IR filter, you can go straight to IR-only capture.

Why would anyone want to do this? Foliage and water can have dramatic shifts when captured in infrared, and make for impressive IR monochromes. As seen by the photos in this gallery, IR imaging can bring out cloud details in an overcast sky or make a building in the background sharp despite atmospheric haze. IR imaging brings to light a world that's hidden just beyond the edges of our vision.

OK, but is this really that easy?

In a word, yes. The reason the IR filter is so easy to remove on the SD14 is to allow the owner to clean their own sensor. This manufacturing choice is an awesome side effect that makes the SD14 one of the few, if not only, hot-swappable IR/visible spectrum SLRs available. Unlike with most other SLRs, which have the IR cutoff just in front of the chip, the IR cutoff filter of the SD14 sits in front of the reflex mirror, and it's a simple process to pop it out. We highly recommend wearing lint-free cotton gloves while removing it to reduce the risk of getting a greasy thumbprint in the middle of the glass for when you re-install it.

Once it's out, you're all set for IR plus visible spectrum photography. We suggest shooting RAW, because even though RAW on the SD14 is ridiculously sluggish, you'll gain much more processing power and exposure latitude when using either Adobe Camera RAW or Sigma's Photo Pro software -- and you'll need to do some major global tweaks to get the images looking good.

Add an IR-exclusive filter, and you'll limit your exposure to IR-only. For these experiments, we used a Cokin 89B filter because that's what we had handy. It transmits at 720nm, but an 87C or other IR-only filter will also do the trick.

IR plus visible and IR-only are two completely different shooting experiences. For IR plus visible, you can frame through the viewfinder. But with IR-only, there's virtually nothing to be seen. Ultra-bright hotspots may bleed through ever-so-slightly, but for the most part it's totally blind shooting. To ensure sharp photos with the Sigma 17-70mm kit lens, we chose hyperfocal distance and stopped down to f/10 to cheese enough depth of field to get almost everything in the frame acceptably sharp.

As with the Fuji UVIR, framing in IR-only mode was accomplished via the ultra-scientific "other eye" method -- hold the camera up to your eye, as if you could see through the IR filter, and frame it with your other eye.

In both IR-plus and IR-only, we found that we were getting the best results at about 2-3 stops underexposure, based on in-camera metering. We found that f/10 1/100 ISO 100 was a good starting point for daytime exposures. You'll probably want to chimp your histograms and also bracket your exposures until you get a feel for it. The LCD preview is going to show a ton of red, but don't worry. Messing around in RAW processing will get them looking good.

We mentioned that you'll have a ton of red in your LCD preview. That's actually good. If you've got a lot of white in the LCD, you're overexposed, and it's tough to fix, especially in JPEG, so again, we remind you to shoot RAW. If you choose to shoot JPEG, don't say we didn't warn you.

The next step is to bring the images into your RAW converter. For black and white conversions, the Monochrome White Balance function of Sigma's Photo Pro software is impressive for both neutral (silver-type) and tinted monochromes. But for color IR plus visible images, Adobe Camera RAW seems to do a better job, particularly with setting color temperature. We found that setting the color temp to around 2600 and desaturating between -33 and -66 yields good global adjustments before importing to Photoshop for final image optimization. Depending on the particulars of the image, you'll probably want to tweak the main exposure adjustment slider during RAW processing.

Once we brought the images into Photoshop, we messed around with most of the commands under Image>Adjustments to get a feel for what worked well with these IR images. Hue/Saturation can selectively desaturate colors even more, or conversely, boost the colors. Shadow/Highlights can pull up blocked shadows. Channel Mixer is probably the strongest monochrome tool in Photoshop, and is an alternative to using Sigma's Monochrome White Balance. Photo filter is good for warming or cooling an image as desired.

We'd tell you there was a formula, but there's not. It's all about experimentation.

With one IR plus visible image, we decided to go two ways, one a full-on monochrome version through Sigma Photo Pro, and the other a false color image via ACR. We then selectively desaturated the blue sky to bring a surreal mood to the same frame. Again, experimentation is a big part of the process.

Sigma is not aggressively marketing the SD14 as one of the only hot-swappable visible, IR plus visible and IR-only spectrum interchangeable lens cameras on the market, but maybe they should. It's a cool trick of this already unconventional, Foveon-sensor based camera. (One of the few others is the Leica M8, but that's another story!)

Stay tuned to Popular Photography & Imaging and for our full lab test of the SD14.


Sigma SD14 Hands On
Sigma SD14 Product Gallery
Sigma SD14 Image Quality Gallery
Sigma SD14 Infrared Image Quality Gallery



Sigma SD14 IR Hack GalleryPhoto By Jack Howard