Digital camera sensors are sensitive to infrared light, which would interfere with the normal photography by confusing the autofocus calculations or softening the image (because infrared light is focused differently than visible light), or oversaturating the red channel. Also, some clothing is transparent in the infrared, leading to unintended (at least to the manufacturer) uses of video cameras.[4] Thus, to improve image quality and protect privacy, many digital cameras employ infrared blockers. Depending on your subject matter, infrared photography may not be practical with these cameras because the exposure times become overly long, often in the range of 30 seconds, creating noise and motion blur in the final image. However, for some subject matter the long exposure does not matter or the motion blur effects actually add to the image. Some lenses will also show a 'hot spot' in the centre of the image as their coatings are optimised for visible light and not for IR.
An alternative method of digital SLR infrared photography is to remove the infrared blocker in front of the CCD and replace it with a filter that removes visible light. This filter is behind the mirror, so the camera can be used normally - handheld, normal shutter speeds, normal composition through the viewfinder, and focus, all work like a normal camera. Metering works but is not always accurate because of the difference between visible and infrared reflection.[5] When the IRblocker is removed, many lenses which did display a hotspot cease to do so, and become perfectly usable for infrared photography.
Since the Bayer filters in most digital cameras absorb a significant fraction of the infrared light, these cameras are sometimes not very sensitive as infrared cameras and can sometimes produce false colors in the images. An alternative approach is to use a Foveon X3 sensor, which does not have absorptive filters on it; the Sigma SD10 DSLR has a removable IR blocking filter and dust protector, which can be simply omitted or replaced by a deep red or complete visible light blocking filter. The result is a very sensitive digital IR camera .
Several Sony cameras have the so-called Night Shot facility, which physically moves the blocking filter away from the light path, which makes the cameras very sensitive to infrared light. Soon after its development, this facility was 'restricted' by Sony to make it difficult for people to take photos that saw through clothing. To do this the iris is opened fully and exposure duration is limited to long times of more than 1/30 second or so. It is possible to shoot infrared but neutral density filters must be used to reduce the camera's sensitivity and the long exposure times mean that care must be taken to avoid camera-shake artefacts.
A Fuji camera has been produced for use in forensic criminology and medicine; it has no blocking filter, and extended ultraviolet sensitivity (digital sensors are usually less sensitive to UV than to IR). The camera, designated the S3 PRO UVIR was only available in the USA and was modified by Fuji US. Optimum UV sensitivity requires special lenses, but ordinary lenses usually work well for IR. Stocks of the S3 are limited because it is due to be replaced by the S5 in 2007, which will limit availability of the UVIR version.[citation needed] In 2007, Fuji has also introduced a non-SLR infrared camera, the IS-1, a modified version of the Fuji FinePix S9100. Unlike the S3 PRO UVIR, the IS-1 does not offer UV sensitivity. This camera is expected to be available internationally, although because of concerns about inappropriate (that is, criminal) use, sales may be restricted to the appropriate professional markets.
Just kidding. I hope you have a speedy recovery.
