The advent of digital photography, and the software that has accompanied this development, has opened up realms of possibilities to the average photographer that were not readily accessible in the good, old days of film. One of these areas is infrared (IR) photography. It is a world of unseen light, as no one knows how it looks. The photographer can create landscape images that have blue skies and golden vegetation, as in the first image in this post, to dark, black and white images, the second image, and almost everything in between, as in the last image below.
In the days of film, you had to have special IR sensitive film, which was expensive when compared to the cost of regular film, an IR filter, a tripod, a remote shutter control, and patience. You had to ensure that the image was properly focused before placing the filter on the lens and you had to be very careful in this part of the operation because if you moved the lens, then you had to remove the filter, refocus the lens, and replace the filter, because you couldn’t see through it. Exposures were measured in seconds and you hoped that what you captured was what you were looking for. When fully exposed, you had to send the film away to a special lab for processing, unless you had the skills and equipment to do your own processing. For those interested, more details on the use of film in IR photography can be found here.
With digital cameras the process has been made much simpler. The filter that sits in front of the sensor that removes IR light can be removed and replaced with one that passes IR light and removes most, or all, of the visible light. The camera can then be used to capture images the same way a regular digital camera does. Post processing of digital IR images is a little different than that of regular colour images and will be covered in a later article.
So, why IR photography? It gives photographers the opportunity to explore the world of unseen light. Light, visible or invisible, is part of the electromagnetic spectrum and its properties are determined by wavelength. Visible light has a wavelength of about 400 to 700 nanometers (billionths of a meter and abbreviated nm). Violet light is found around the 400nm wavelength and red light is found around the 700nm wavelength. IR light starts around 700nm and goes up to about 1200nm. None of this light is visible to the human eye without help (e.g., with night vision goggles). IR light is often divided into near IR, mid-IR and far IR, and IR photography is confined to the near IR spectrum, roughly 700 to 900nm. Most companies offering IR conversions for digital cameras will offer a choice of replacement filters that cover this range. However, only one filter can be used in a single camera. If you want the option of using more than one filter you will probably need to have more than one camera converted, although this can sometimes be circumvented with software. I will cover more about this in an upcoming article.
This is the first of four articles on infrared photography. You can read part two here.