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Welcome to the exciting world of High dynamic range imaging.

In computer graphics and photography, high dynamic range imaging (HDRI) is a set of techniques that allow a far greater dynamic range of exposures (i.e. a large difference between light and dark areas) than normal digital imaging techniques. The intention of HDRI is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to the deepest shadows.

The use of high dynamic range imaging in computer graphics was pioneered by Paul Debevec. Debevec is thought to be the first person to create computer graphic images using HDRI maps to realistically light and animate computer graphics objects. Gregory Ward created the Radiance RGBE image file format in 1985, which was the first and still is the most commonly used file format for high dynamic range imaging today.

Tone mapping

One problem with HDR has always been in viewing the images. CRTs, LCDs, prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of "converting" HDR images into a viewable format have been developed, generally called "tone mapping".

Early methods of tone mapping were simple. They simply showed a "window" of the entire dynamic range, clipping to set minimum and maximum values. However, more recent methods have attempted to show more of the dynamic range. The more complex methods tap into research on how the human eye and visual cortex perceive a scene, trying to show the whole dynamic range while retaining realistic colour and contrast.

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