Light is electromagnetic radiation. In particular it’s that part of the electromagnetic spectrum that our eyes are sensitive to: it ranges in wavelength from about 400nm (violet) to 700nm (red). Beyond red light we come to infrared (IR). Like ordinary light, infrared (or specifically near infrared) can be focussed by glass lenses and recorded by the CCD in a digital camera.
Infrared photography can be used to produce interesting ghostly effects, but all cameras are different so test yours before buying any pricey gear. (Click the photo for a high resolution version.)
By excluding all visible light from the camera while allowing infrared to pass, it’s possible to take photographs using infrared alone. White clouds can appear against an almost black sky and green vegetation comes out so white that it almost glows. The end result has been variously described as otherworldly, ethereal and ghostly.
If you don’t want to fake the effect (see ‘Fake Infrared Ektachrome’ later in the article), you’ll need to collect together a little bit of kit to do this right. First, infrared photographs usually require a long exposure so you’ll need a tripod. However, if you don’t already have one, hold off on buying one until you’ve tried a test infrared photograph. If you just happen to have a camera that’s unusually sensitive to infrared you might get away with using it handheld, but it’s unlikely. Small tripods start at about £10.
Choosing a filter
The next consideration is an infrared filter. For your first attempts at infrared photography we suggested that you use the Hoya R72 filter. Its cut-off point is only just into the infrared spectrum, which means it actually lets a small amount of visible red light through too. If you’re pleased with your initial foray into infrared photograph and want to go one stage further, you could try other infrared filters that have cut-off points further into the infrared spectrum. The infrared effect will be even more pronounced and dramatic, but exposure times will be increased.
The Hoya R72 has a 50 per cent cut-off point of 720nm. The Kodak Wratten #87 has a corresponding figure of 795nm and excludes all visible light. The Wratten #87C has an 850nm 50 per cent cut-off and this is probably as far as you’d want to go. Although Wratten filters are supplied as 75mm square gelatine sheets that aren’t easy to attach to your lens, manufacturers of screw-in filters often refer to an equivalent Wratten number.
But before you buy, make sure it’s actually going to work with your camera…
Preparatory work
Although CCDs are extremely sensitive to infrared, many digital cameras aren’t. This is because manufacturers usually put a filter in the camera to block infrared, as it would otherwise upset the colour balance. These filters aren’t 100 per cent effective so some infrared still reaches the CCD, but exactly how sensitive a camera is to infrared varies greatly. Your first job is to check that your camera is sensitive enough to be usable.
The unusually high reflectivity of grass and foliage is responsible for the unreal look of infrared photographs. (Click the photo for a high resolution version.)
The easiest way to do this is to ask a local photographic shop if you can try an infrared filter before you buy. Here we’re talking about a filter that allows infrared to pass through while blocking visible light. Remember that the light meter might be wildly inaccurate under these conditions, so if you don’t get an image on your first attempt, try over-exposing by several stops if necessary. Another option is to use a TV or DVD remote control unit, since all such devices emit infrared light. If your camera allows the LCD panel to be used as a viewfinder, view the infrared emitter at the front end of the remote on the LCD panel and press one of the remote’s buttons in a dark room. A bright dot indicates that the camera has reasonable infrared sensitivity. If you have a digital SLR that can’t use its LCD panel as a viewfinder you’ll have to try a test photograph, again bearing in mind that you might have to over-expose.
Once you’ve discovered that your camera can be used for infrared photography and bought an infrared filter, you can start to get a better feel for what sort of exposure you’ll need under various conditions. Screw the filter onto your lens and try some test shots. The exposure will be much longer than normal and could be several seconds, even on a bright day. On the basis of these trials you can decide whether there’s any chance of shooting handheld or if you’ll need to use a tripod. The other piece of information you’ll glean from this test is whether the camera’s light meter is accurate in infrared and, if not, by how much you’ll need to over-expose.
Capturing the invisible
If you’ve got this far we’ll assume that you have an adequately sensitive camera, have bought an infrared filter and have decided whether you need to use a tripod. Now you’re ready to pack your gear up and try your hand at some infrared photography. First, though, a word on your choice of a subject.
We don’t want to be too prescriptive because this can stifle creativity, but perhaps we can offer a few suggestions to get you started. Remember the unique characteristics of infrared photographs – the blackening of blue skies and ghostly white rendering of grass and tree leaves – and pick your scene accordingly. Trees in the summer against a blue sky might look quite dramatic whereas an overcast scene of a bracken-covered moor almost certainly won’t. Try looking at the work of others for inspiration – you’ll find no shortage of infrared photo galleries on the web. You’ll soon see that some subjects seem to work whereas other just don’t, and you’ll also discover that some scenes are almost compulsory for infrared photographers. Perhaps the all-time favourite cliché is the graveyard, which seems to be perfectly suited to the ghostly look of infrared.
This might be a cliché, but every infrared photographer has to shoot a graveyard sooner or later. (Click the photo for a high resolution version.)
Taking a shot should now be plain sailing but there’s one possible snag – you might not be able to see anything in the viewfinder with the infrared filter attached. If you have an independent optical viewfinder you’ll be OK, but you may or may not be able to see the scene in an LCD viewfinder, depending on the camera. With a conventional DSLR the viewfinder will almost certainly be blank. If you aren’t able to see through the viewfinder, you’ll have to frame the shot before fixing the filter –so you’ll have to use a tripod.
Infrared photographs will rarely be up to scratch straight out of the camera, so image processing will almost always be necessary. First, although infrared photograph is a form of black-and-white photography, your photograph probably has some colour cast. Often the raw photograph will be in shades or red, so your first job is to convert it to greyscale. Even if the result does appear to be black and white, you should still to convert it to greyscale to ensure accurate blacks and whites. Then, because high contrast is often important in infrared photography, you might decide to exaggerate it by artificially increasing the contrast. Ensure you only ever edit a copy – leave the original intact so that you can try something different later if you want.
Infrared colour photography
Infrared is normally considered a form of black-and-white photography, so infrared colour photography sounds like a contradiction in terms. However, it’s possible to create a photograph that contains some colour information yet has the tonal quality of an infrared photograph.
First, take a pair of photographs of the scene, one in infrared and the other normally in visible light. This means that the camera must be mounted on a tripod and that nothing in shot is moving. It’s also important to use the same aperture for the two shots so that the depth of field is the same. Try to work as quickly as possible so that the lighting or slow-moving clouds don’t change much between the shots. You need to add or remove a filter between shots and probably alter the exposure, which could be tricky. It’s a good idea to give this process a bit of thought before trying it out for real.
Process the infrared photograph as already described for ordinary infrared photography. Now, using your photo-editing software, split the ordinary photograph into either the HLS (Hue, Lightness, Saturation) or HSB (Hue, Saturation, Brightness) channels – the two are slightly different so try experimenting with both. Splitting channels is a feature of most fully featured photo editing packages, although it might be absent on entry-level products. Each channel appears as a greyscale image, of which one – lightness or brightness – defines the lightness. Since we want to impart the tonal qualities of an infrared image, discard the brightness or lightness channel and put the infrared image in its place before recombining the channels. The result should be quite an eye-opener.
Combining an ordinary photograph with an infrared shot can create dramatic colour effects. (Click the photo for a high resolution version.)
This is just one way of creating a colour infrared image and the possibilities are limited only by your imagination. Here’s another method that has been widely used, but be aware that the exact result will differ from one camera to another – so you might end up with a different effect entirely. And if the infrared image as it comes out of your camera appears black and white this method won’t work at all. Take an infrared photograph but, instead of converting it to a greyscale image, use your photo manipulation package to correct the white balance. Although the colours won’t be correct it will result in some parts of the photograph coming out almost white instead of shades of pink. The sky will appear red or brown, which looks most odd. To correct this you need to use the channel splitting and recombining trick. But instead of splitting to HLS or HSB, split the photograph to RGB (Red, Green, Blue) and then recombine with the Red and Blue channels swapped. With a bit of luck you’ll end up with a blue sky, while any foliage will have a slight sepia hue to its ghostly appearance.
Fake an infrared photograph
For many, the appeal of infrared photography is that it’s a natural phenomenon that can’t be recreated by digital wizardry. However, if you don’t want to shell out on an infrared filter you can get a similar (albeit less dramatic) effect using image-processing software.
Take an ordinary colour photograph and make sure it’s one with a really dark blue sky and light, well-lit foliage. Using your photo-editing software, split the channels to RGB and then discard the blue channel, recombine the remaining two channels and convert to greyscale. This will have the same effect as putting a red filter on the camera – it darkens the sky but not as dramatically as happens with an infrared filter. The glowing white appearance of the foliage will be absent, though, so let’s try something different. Again split the colour photograph to RGB and discard the blue channel. Before recombining, though, try increasing the brightness of the green channel. Now when you recombine you’ll find that the foliage has become lighter but, because all but the darkest azure blue skies contain some green content, the sky won’t be as dark. A degree of trial and error is required to find a compromise that comes close to the genuine infrared effect.
Simulate infrared ektachrome
For many years Kodak produced a film called Infrared Ektachrome, which produced a colour infrared image. That image was very different from the colour images we’ve discussed in the main part of this article because the film was intended for scientific rather than artistic purposes. Nevertheless, some mainstream photographers did experiment with it for its novelty value, and it’s quite possible to emulate it digitally.
An ordinary colour photograph is made up of images in the three primary colours – red, green and blue. Infrared can be though of as another colour so Infrared Ektachrome recorded an image in three alternative primary colours – infrared, red and green. Because our eyes can’t see the infrared, each primary colour was translated so that infrared appeared as red, red as green and green as blue. Because our eyes can only handle three primary colours, blue was discarded by putting a yellow filter over the lens. This combination of infrared and colour was used in aerial photography because it showed up features than couldn’t be seen in visible light alone. Normal crops, for example, appeared red because they’re highly reflective of infrared whereas diseased crops looked blue because they only reflected green light.
A different way of combining a visible and an infrared shot gives results reminiscent of Infrared Ektachrome film. (Click the photo for a high resolution version.)
To create this effect you need to take a pair of photographs, one in visible light and one in the infrared and combine them in a photo manipulation package. This time, however, split the visible image to RGB, discard the blue channel and recombine with the infrared image in place or the red channel, the red in place of the green, and the green in place of the blue.
Near and far
Infrared photography is often thought as a means of seeing in the dark. But the far infrared radiation (or heat) emitted by living creatures, is recorded. It’s also possible to use near infrared to photograph in the dark, but because most objects don’t emit near infrared you need a source of infrared illumination. A flashgun with an infrared filter over it will do nicely.
Although many insects can see ultraviolet, few creatures have vision that extends into the infrared. Research has suggested that birds of prey can see longer wavelengths than humans, but they probably don’t perceive this near infrared as an extra colour – so you have the potential to capture scenes that no living creature has ever seen.
