
1
Introduction
The computer graphics and related industries, in particular those involved
with films, games, simulation, virtual reality, and military applications,
continue to demand more realistic images displayed on a computer, that
is, synthesized images that more accurately match the real scene they are
intended to represent. This is particularly challenging when considering im-
ages of the natural world that present our visual system with a wide range
of colors and intensities. A starlit night has an average luminance level of
around 10
−3
cd/m
2
, and daylight scenes are close to 10
6
cd/m
2
.Humans
can see detail in regions that vary by 1:10
4
at any giv ...