Infrared photography literally allows you to create images in a different light. Without getting too technical light is measured in nanometres, the wavelength of light that we as humans can see starts at around 400nm (nanometres) this being the blue end of the visible spectrum and goes up to around 700nm this being the red end of the visible spectrum. Below 400nm we have the invisible ultraviolet light; above 700nm we have the invisible near infrared light, the bit we as photographers are interested in.
How do we record this near infrared light? In the past I used infrared film to record monochrome images, and this is still available for those using film. It is however quite easy to take infrared images using your digital camera. Surprisingly many of the sensors used in digital cameras are more sensitive to near infrared light than infrared film. In more expensive cameras, manufacturers go to great lengths to block this sensitivity by placing a filter on the sensor to try and minimise the amount of infrared it records, this is often referred to as a hot filter.
To record our infrared photograph we first need to stop our camera from recording the visible spectrum. This is done by fitting an infrared filter which blocks most of the visible spectrum only allowing light from about 700nm upwards to pass and record on the sensor. Infrared filters are easy to source and are made by most filter manufacturers; popular ones are made by Hoya and Kood. Cokin also make them for the square filter systems. To check if your digital camera will record infrared you need to place the filter over the lens to block the visible light. You can then use your TV remote which uses a beam of infrared light to control the TV to test the camera. Get someone to point the remote at your digital camera with its IR filter fitted and press the remote as if controlling the TV, if a white light can be seen emanating from your TV remote then your camera is seeing the infrared light and will be capable of recording infrared photographs. It may be wise to borrow an infrared filter to test your camera they are quite expensive to buy especially in larger filter sizes.
What are the drawbacks of using your digital camera to take infrared pictures?
The main drawback is the infrared filter, it is opaque to the human eye, this is because it is blocking the visible light. Because of this if you use an SLR you need to put your camera on a tripod and frame up your picture first then fit the filter, once the filter is fitted you will see nothing through the viewfinder. If you are using a camera with an electronic viewfinder such as a bridge camera, or using a screen to view your scene then you should have a visible image but it will look quite dull and have a heavy red cast. Another drawback is the length of your exposure, because your sensor will have a hot filter of some sort fitted its sensitivity to IR has been greatly reduced so it takes much longer to record an image in IR, Expect exposure times to be long, especially at small apertures, exposure can be 40seconds or even more. This will of course depend on the sensitivity of your sensor and the effectiveness of your hot filter. Some of the earlier digital cameras were very sensitive to infrared. There are lots of articles on the internet that discuss these topics.
There is a different way to tackle taking IR pictures which is more effective; this involves removing the hot filter from the sensor and replacing it with an IR filter mounted directly on the sensor. Unless you are very competent I would advise having this done professionally you can easily wreck your camera. It is not a cheap option expect to pay at least £300 for an SLR camera conversion. There are instructions on the internet for converting your own camera if you really want to take that risk. The benefit of an IR conversion is that you can shoot hand held at similar settings to photographing with the visible spectrum and if you are using an SLR your viewfinder works exactly the same as it does for visible light photography. The down side is that the camera can now only shoot IR and is no use at all for conventional visible light photography.
I have only explained the possibility of using a digital camera to take infrared photographs if you want to know more I can point you to at least a few book titles.
Digital Infrared Photography by Cyrill Harnischmacher Published by Rockynook
Digital Infrared Photography Photo Workshop by Deborah Sandidge Published by Wiley ISBN: 978-0-470-40521-5
Digital Infrared Pro Secrets by David D Busch Published by Thompson Course Technology ISBN-13:978-1-59863-355-9
Complete Guide to Digital Infrared Photography Joe Farace Published by Lark Books
I would also look at Infrared Photography a Complete Workshop Guide by Hugh Milsom ISBN 0 86343 373 1 This wonderful book was written with traditional infrared film photography in mind but so much of it is also relevant for the digital photographer.
If you want to view some really nice IR images taken with film look at Kathy Harcom’s work on line or in her book, Light sensitive ISBN 1-904825-01-X
This may be difficult to find as the publisher no longer operates, it may however be available from her own website.
Alternatively you could contact me via Lancaster Photographic Society’s web site if you have any queries.