Getting Started with Digital IR Photography

2009-08-01

Infrared photography has never been easy, but once upon a time it was at least straightforward. You bought a roll of infrared film (typically Kodak High Speed Infrared, variously called HSI or HIE, for black & white or Kodak Ektachrome Infrared, EIR, for color), attached an appropriate filter (deep red, infrared, or yellow), and started taking pictures. Okay, admittedly, it was never really that simple. Your camera had to be sufficiently old-fashioned as to not have an infrared film sensor, the film had to be loaded in absolute darkness, and exposure bracketing was mandatory, giving you at best 12 usable images from a $15-$25 36exp roll. But still, the process was fairly straightforward.

Then, last year, Kodak announced that it was discontinuing its 35mm infrared films. Remaining supplies were snatched up quickly, sometimes being resold for 10x their retail price. (I actually saw a roll of Kodak EIR on eBay for over US$200.) What was an infrared photographer to do?

As it turns out, the sensors used in digital cameras are inherently sensitive to infrared, with a spectral range of about 350nm to about 1000nm. Meanwhile, visible light mainly falls between 400 and 700nm. To accomodate this, all consumer digital cameras have an infrared blocking filter in front of their sensors. If you take one of these cameras and place an infrared low pass filter in front of the lens, the result will be equivalent to using the infrared-passing filter and several neutral density filters at once: you’ll be able to get infrared photos, but only with exposures on the order of 2-30 seconds. But while this might be acceptable for landscape work on a calm day, it’s completely out of the question for the kind of work I had been getting into at the time: infrared nudes.

Luckily, there was another option: remove the infrared blocking filter from the sensor. There are a number of outfits that offer this service, with the two largest being MaxMax (aka LDP) and LifePixel. Both companies offer the option of converting the camera to IR-only (though each with slightly different IR options) or to UV+Vis+IR (sometimes called Full Spectrum). Essentially they’ll either replace the infrared blocking filter in your camera with a filter that blocks visible light instead or with a piece of clear glass. (Simply removing the filter entirely would affect the focal plane of the camera causing blurry images.)

As an aside, despite LifePixel’s fancier website and 25% lower price, I chose to go with MaxMax because they were more responsive to my inquiries (in fact, I was never able to reach LifePixel by phone) and because their site contained a substantial amount of information about the conversion process, filters, etc. I was personally extremely satisfied with their service but, of course, YMMV.

Regardless of who you choose to do your conversion, there are pros and cons to both approaches. By placing the infrared filter internally, you are still able to use the viewfinder in the camera, which is a big advantage. In the days of film, one of the major difficulties of using a true infrared filter was that it would prevent use of the viewfinder by blocking all visible light from entering the lens in the first place. On the other hand, once a camera is converted to infrared-only in this way, taking visible light images becomes impossible. You are also limited to the filter you have installed, which eliminates the creative freedom available by selecting different filters for diffierent photographs.

In the end, I found a solution. A few newer digital SLRs come with a feature that has been present on pocket digital cameras since they first came on the market: the ability to see what the sensor sees in real time on the LCD display, thus allowing you to use an opaque filter in front of the lens without reducing your ability to compose the photo. The Canon Rebel XSi was one of the first of these, and that’s the camera I chose to purchase and convert to UV+Vis+IR.

In a future post, I will discuss the wide variety of filters available for infrared photography, including how filters can be used to let you take normal color photographs with a full spectrum camera.

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