Filters, Internal & External Infra-Red

Because infra-red radiation contaminates images taken under normal conditions modern day digital cameras are fitted with a cut filter, placed in front of the censor to filter out most, if not all infra-red wavelength's. However, some digital cameras are still quite sensitive to Infra-red even with this cut filter firmly in place, notably the Nikon D50, although exposure times will be quite long, even under bright conditions.

If you only ever use your camera for taking infra-red images you may consider having the cut filter completely removed and an infra-red filter put in it's place. The benefit of this procedure is two fold, first, exposure times will be greatly reduced, from seconds to fractions of a second and secondly, you will be able to see the scene before you, in the camera's viewfinder window, all be it slightly reddish.

If, like me, you are happy enough to leave your cut filter in place and not have your camera modified you will have to place an infra-red filter across the front of your lens. The filter I use is made by Hoya, an R72 type. The R72 will block out normal wavelength's below 720nm.

Composition of your subject is made without the filter in place, for the simple reason, the filter is opaque and you can't see though it. With your camera firmly fixed to a tripod, compose your shot in the normal way and refit the filter before making your exposure.

Use the Infra-red Archive to discover more about the world of Infra-red Photography