HDR Image Capture

HDR images may be captured from real scenes or rendered using 3D computer graphics (CG) techniques such as radiosity and raytracing. A few modern graphics cards are even capable of generating HDR images directly.

A camera is essentially an imperfect device for measuring the radiance distrubition of a scene, in that it cannot capture the full spectral content and dynamic range. The film or image sensor in a conventional or digital camera is exposed to the color and dynamic range of a scene, as the lens is a passive element that merely refocuses the incoming light onto the image plane.

Source - High Dynamic Range Imaging: Acquisition, Display and Image-Based Lighting
(Erik Reinhard, Greg Ward, Sumanta Pattanaik, Paul Debevec)