HDRR

http://en.wikipedia.org/wiki/High_dynamic_range_rendering

Without HDRR, the sun and most lights are clipped to 100% (1.0 in the framebuffer). When this light is reflected the result must then be less than or equal to 1, since the reflected value is calculated by multiplying the original value by the surface reflectiveness, usually in the range 0 to 1. This gives the impression that the scene is dull or bland. However, using HDRR, the light produced by the sun and other lights can be represented with appropriately high values, exceeding the 1.0 clamping limit in the frame buffer, with the sun possibly being stored as high as 60000. When the light from them is reflected it will remain relatively high (even for very poor reflectors), which will be clipped to white or properly tonemapped when rendered.