In Infrared photography, a filter that blocks most of the visible light spectrum and only lets infrared (IR) light pass through, is used.
When these filters are used together with infrared sensitive film or sensors, this results in very interesting false-color or black and white images with a fairy tale appearance.
The effect is mainly caused by foliage (like tree leaves and grass) strongly reflecting and emitting (through fluorescence) infrared and thus appearing very bright, while other objects like water turn black.
Digital camera sensors are usually sensitive to infrared and the infrared will interfere with the normal photography.
This might confuse the autofocus algorithm, oversaturate the red channel or soften the image because IR light is focussed differently through the lens than normal light. Thus, to improve the image quality, some digital cameras employ infrared blockers.
Infrared photography is usually not practical with these cameras because the exposure times become overly long, creating noise and motion blur in the final image.
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