Infrared is a type of light, invisible to the human eye, that lies just beyond the red end of the visible spectrum. Unlike the eye, however, most digital cameras are sensitive to infrared, providing us with a means of seeing the invisible.
Infrared photography is used in agriculture, mineral prospecting and ecology because it reveals hidden information. But it’s also fascinating for the rest of us because it produces such strange-looking results.
Trees and grass are so bright they almost glow, while blue skies come out virtually black and clouds remain white. The bizarre properties of infrared produce results that are ghostly, ethereal, eerie and other-worldly.
In this walkthrough we’ve used Corel Photo-Paint X3 to process the images. Other photo-editing suites will offer similar functions, but some entry-level packages don’t include the channel-splitting features you’ll need in the later steps.
1. First, check your camera can record infrared. Point a TV remote at the lens in a dark room and press a button (on the remote). If you can see a bright spot on the LCD viewfinder, your camera is recording the infrared. Most SLRs can’t preview on the LCD so you’ll need to actually take a photo.
2. To take infrared shots, your camera will need a filter that excludes visible light. A glass filter will set you back £20; for a cheap alternative, sandwich a circle of gel filter between two second-hand skylight filters from a good camera shop.
3. To discover how your camera responds to infrared – and what exposure to use – attach the infrared filter and try a test shot in programmed automatic mode. Some cameras will produce good-looking results in this mode. If yours doesn’t, try overexposing more and more until the shot looks right.
4. Now you’re ready to shoot. If the results of step 3 indicate that you need to overexpose to get good shots, consider a high ISO rating – this will reduce the exposure time but increase image noise. If you want to minimise noise or if your camera requires a long exposure even with a high ISO, use a tripod.
5. Some cameras produce infrared photographs with a heavy colour cast – normally red or magenta. Even if yours is producing apparently colour-free pics, you need to convert them to proper black-and-white images. Open the image and select ‘Convert to Grayscale (8-bit)’ from the Image menu.
6. Black-and-white photographs tend to look more attractive if they have high contrast. Select Brightness/Contrast/Intensity from the Adjust menu, then adjust the Contrast slider until you see the effect you want. You might have to adjust Brightness and Intensity too. Click ok when things look right.
7. Although you’d normally want to minimise image noise, some infrared photographers like noise because it emulates the grain of infrared film. To add this effect, select Noise, Add Noise from the Effects menu. Now adjust the controls until you get the desired effect and click ok.
8. To add colour to an infrared shot, you can combine an infrared photograph (with the filter in place) with one taken normally. The shots must match perfectly, so use a tripod and don’t move it between exposures. Use aperture priority or manual exposure so the aperture is the same. Ideally, you should shoot RAW or Tiff images.
9. Our first colour technique duplicates Kodak’s Infrared Ektachrome film, which reproduces infrared as red, red as green and green as blue. Open the normal image and select Image, Split Channels to, RGB. Three new images will appear, showing the red, green and blue content of the original image respectively.
10. We’re not going to use the blue image, so close it without saving. Now open the matching infrared photograph. Convert it to monochrome and adjust the contrast as you did in steps 5 and 6. Next, we can combine the infrared, red and green images into a false-colour photograph.
11. Select Image, Combine Channels and choose RGB as the mode in the Combine dialog box. Select R as the channel and browse to your infrared image in the image list. Then choose G as the channel and the red picture from the list. Finally select B as the channel and the green image. Click ok, and you’re done.
12. This type of colour infrared photograph is interesting because it reveals details that can’t normally be seen. To the untrained eye, however, it looks like yet another false-colour image produced by digital manipulation. For a more artistic way of introducing colour, split channels as in Step 9 but choose YIQ instead of RGB.
13. The I and Q images contain the colour information and the Y image contains the intensities. Substitute the infrared shot for the Y image and you should end up with correct colours but the tonal properties of an infrared photograph. Close the Y image and open the infrared one. Convert it as before and adjust the contrast.
14. Select Image, Combine Channels and choose YIQ as the mode in the Combine dialog box. Select Y as the channel and your infrared image from the list of images. Next, choose I as the channel and the I image from the list. Finally, select Q as the channel and the Q image from the list. Click ok.