Art of invisible light – Infra Red & Foveon

Art of invisible light – Infra Red & Foveon

Infra-red photography was full of challenges in the days of film and, until recently, almost impossible with modern digital cameras. It’s a little known fact that, with the latest Sigma digital SLRs, the ability to capture IR images has become somewhat easier. Richard Kilpatrick looks at the possibilities.

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IR/Near-IR photography yields very different results for a scene due to the way IR interacts with man-made and natural elements. Here the church is in bright light, and the sky is blue – yet the sky, reflecting no IR, is dark whilst the clouds are bright, as are the leaves on the bush in direct sunlight. The church reflects no IR, and appears dark.
For most DSLR users, the best they can hope to get is “near IR” without expensive modifications; some models are better at filtering it out than others (one of the technical differences that can lead to differing “feel” for portraiture and colours); Sigma have always included a removable IR-cut filter in the form of the dust protector visible when the lens is removed. On early models, this required a screwdriver to remove; since the SD14 the mirror has been a simple “click” operation – clean hands and as dust-free an environment as possible are vital of course, as without the filter in place the sensor is more exposed than a typical DSLR with low-pass and IR filter glass as part of the assembly.

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Refitting should be performed with lint-free gloves, but even with those do not be tempted to refit the cover touching the glass. If you line it up correctly, the housing will click back into place easily; a broken filter is easily and inexpensively replaced but may leave microscopic material in the mirror box, and is an unwelcome nuisance and cost.
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Before desaturation, the captured image looks like the one above. Below is the monochrome IR photograph; no processing is needed to get this result, though you may choose to apply curves and adjustments to suit your intended look.
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The removable filter has been carried through from the original SD9 and 10, where it had to be removed with screws, to the SD14, 15 and new 15.4Mp X3 SD1. Crucially with the SD1, the native resolution is large enough for a near 20×30″ print.
Mixed visible and IR is tricky to balance, due to the overall sensitivity of the Foveon and the sheer amount of IR in the environment; for a successful introduction to IR photography it’s simpler to work with pure NIR, by installing a filter which blocks visible light. Here’s a KOOD R72 unit, which presented some limitations in the lenses I could use due to the 77mm thread. It’s a good idea to buy a 77mm if your budget is limited, as it’s easily adapted for 72mm – 82mm, though obviously matched filters will allow the use of hoods.
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For framing with nothing visible in the viewfinder, I use an “Ikodot” (previously covered here as an alternative finder for the DP1)
 

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Above: The image preview is tinted by the filter, but as the histogram shows, the exposure times are not particularly long – you can shoot handheld. Below Left, the Ikodot used for framing and composition, and below right, a full size image preview. Burned out highlights are very obvious when you get them; the image may look dark but when converted to monochrome you will see the texture the Sigma retains even in foliage.
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If this seems like a remarkably short article for IR, you can thank the Sigma SD’s simple way of making it possible – taking the shot is easy and no special processing is required for straightforward, good monochrome results. The rest is up to your creativity.