Digital Infrared Photography

Galway Cathedral as seen from across the river Corrib and by Salmon Wier bridge.

Two years ago, I posted some information about taking digital infrared images – a short tutorial based on my own experiences thus far . This summer (and yes, occasionally, there was a bit of summer in 2008), I have taken a lot of infrared (IR) images, so I thought I might as well update the tutorial.

Digital infrared photography requires an infrared filter to be fixed to the front of the lens, in the same way as a UV (ultraviolet) filter or a polarising filter. The filter is a very deep red (almost black) and is nearly opaque. Having an IR filter in your camera bag is a bit of a luxury – IR filters are much more expensive than UV or polarising filters, and it is unlikely that you’ll get much use from it. Until this year, my IR equipment was a bit of a compromise. I was using a Hoya R72 which has a 58mm filter thread – i.e. it only fitted on lenses that were 58mm wide at the front. The problem for me was that, when I bought my Canon 5D, I bought two Canon L-series lens – they are very good but they have a 77mm filter thread. At the time, I didn’t fancy buying another filter, so I used an old Sigma 28-70mm lens that I had bought a decade ago with my old film EOS camera. The Sigma lens was only barely compatible with the 5D – I could take pictures but the lens would only work at the widest aperture (f4.5). The shallow depth of field meant that sometimes, parts of a composition were out of focus. As a result, I didn’t take many IR pictures.

In February this year, I was in New York, and like every other tourist with an interest in photography, I went to B&H Photo . There, I bought a Tiffen 87 IR filter with a 77mm thread (actually, I bought lots of things there but that’s another story). The Tiffen 87 is a darker filter than the Hoya R72, so it requires longer exposure times.

I use my Canon 24-105mm L lens for most of my outdoor pictures, fitted to a Canon 5D DSLR. I always use a tripod to compose the image because the filter blocks so much light that a very slow shutter speed is required. It’s also good to use a remote shutter release – if you don’t have one, just use the self-timer on the camera.

The first step is to compose the image. I make sure that the Image Stabilizer is switched off on the lens (it can cause blurring when the camera is fixed to a tripod) and also make sure that the tripod is steady on the ground (you need to be sure that a light wind will not cause the camera to shake even slightly). I like to use a high aperture – at least f8 but usually f11 or higher. The reason is that the autofocus does not always work when the filter is covering the lens, requiring manual focus instead. In such cases, the higher the aperture, the better. I also have a Canon 40D and thought that I might be able to use the camera’s Live View to compose when the IR filter is fitted. Alas, the filter is too dark, and nothing appears on the Live View screen.

Because the IR filter is red, the final image will have a deep red tint. I use the Custom White Balance (CMB) function on the camera to counteract the red tint. The White Balance function allows the user to counteract the effect of colour tints cause by either light sources (e.g. flourescent lighting) or from filters. The CWB allows one to set the White Balance manually (i.e. to identify a light source that the camera exposure meter can identify as white) . An easy way, for IR photography, is to take an image (with the filter on ) of something neutral, such as grass, and then use that image as the sample image for the CWB function. There is an even simpler way of setting the CWB. Compose your picture and then take a shot (with the camera set to Automatic White Balance, which is my default setting) with the filter on. You’ll see on the camera’s LCD that it is heavily tinted red. Use that image as the CWB image and take another shot – the image will be prefectly colour balanced for a monochrome image).

I usually try to keep the ISO at 400. Setting it lower (e.g ISO 100 or 200) results in very long exposure times, and setting it higher (ISO 800 or above) means the image will be very grainy – you’re going to get more ‘grain’ in any case using the IR filter. I judge the exposure times from test images rather than in-camera metering. On a sunny day, an exposure will take around 15 seconds (at f8 at ISO400), but I’ve had to go as high as 25 or 30 seconds depending on the light.

It’s essential to ensure no light enters the viewfinder/eyepiece during the exposure – otherwise, the image will be fogged (you’ll see a light band or streak on the image). To prevent this you can hold your finger or thumb against the eyepiece. Since there is danger that you might nudge the camera and blur the image, the alternative (on Canon cameras at least) is to use an accessory that is supplied with the camera-strap. The accessory slides over the eyepiece and blocks all light.

It’s always a good idea to check the image on the LCD on the camera back after taking a picture, since it is easy to forget one of the steps. I often shoot a normal image as well as an IR version of the same composition, and I sometimes forget to reset the White Balance or block the eyepiece.

I post-process my images in Lightroom 2 – I convert to grayscale and then adjust the light and dark areas of the image to improve tonal contrast. The other thing you need is some sunshine, since it lowers the exposure time and also increases the contrast of the image. This year, that turned out to be the hardest thing to achieve.

Camera = Canon 5D, lens = 24-105 @ 24mm, aperture = f8, speed = 25 sec, ISO=400, tripod.

Buy this picture and other black and white images of Galway City.