Pixiq

Digital photography has greatly simplified IR monochrome image-making by offering three approaches. First, because the sensors in all digital cameras are sensitive to IR light, it is possible to capture subjects in this light if the visible light spectrum is blocked. Some manufacturers, however, add an IR blocking filter to their sensors. A simple test to determine if such a filter is in place is to shine the infrared beam of a television remote at the camera and take a picture. If the camera records the beam, the sensor does not have a blocking filter. Now placing a visible light-blocking filter such as an #87 or #89 filter over the lens will record what IR light is present. This was the case in example A below.

In the case of a D-SLR with an optical viewfinder, the view of the scene will be completely blocked by these filters, and the longer exposure times make the use of a tripod necessary. So this approach eliminates the inconvenience of loading and unloading film in total darkness but still has the limitations of a blacked-out viewfinder and slow exposure times. Nevertheless, the ability to obtain IR images instantly is most exciting.

A small number of digital SLR cameras use a design that transmits a video image to the viewfinder instead of the more common optical pathway. Assuming no IR blocking filter is in place, when a visible light spectrum filter is placed on the lens, the infrared picture that will be captured can be seen in the video viewfinder. Otherwise, when a light-blocking filter is used, the photographer has to rely on the small LCD camera screen as a representation of the captured IR image. The LCD display will show the infrared picture with some coloration. This colorcast is removed later in the computer by desaturating the image for a full-tone neutral black and white IR image, as seen in example B.

The second and much more convenient approach to digital IR photography is to have a digital SLR camera converted so that it only records infrared light. Such custom conversions are available from a number of sources for certain SLR models. Once converted, there is no need to use a light-blocking filter, leaving the viewfinder fully operational. These converted cameras can also make use of their full ISO range, taking pictures at shutter speeds and apertures roughly the same as with visible light and with accurate autofocus capabilities. IR light focuses at a different point than visible light. So, with an unaltered camera, adjustments have to be made in the way the lens is focused. This means being able to photograph moving subjects at action-freezing shutter speeds without the need for a tripod. Another alternative is to consider purchasing one of the IR-type cameras now being marketed by Fujifilm Corporation. Depending on the mode and the filters used, it is possible to produce not only a black-and-white IR image but also various IR color versions.

The third approach to obtaining an IR image is to use software to convert a color image to a black-and-white infrared look. This can be done either in a sophisticated general imaging software program or through the use of specialized IR plug-in programs such as the nik Color Efex Pro software “IR B&W Filter” or the “SilverIR” filter from Silver Oxide software. 

When using a general image-processing program, the usual approach is to use the channel-mixer function to mimic the way colors are converted to black-and-white tones in IR light, especially the rendering of green foliage as white and blue skies as black. Then a degree of softness can be added, along with some glow effects. A number of IR enthusiast websites describe these techniques in detail, along with more information about the camera conversions and use of light blocking filter.