Graphics Reference
In-Depth Information
glare. The tone mapping algorithm used for these images is described in the pa-
per “A Visibility Matching Tone Reproduction Operator for High Dynamic Range
Scenes” by Ward, Holly Rushmeier, and Christine Piatko [Ward Larson et al. 97].
In 2002, a new tone mapping method was presented in the paper “Photo-
graphic Tone Reproduction for Digital Images” by Erik Reinhard, Michael M.
Stark, Peter Shirley, and James Ferwerda [Reinhard et al. 02]. The method de-
scribed in this paper applied photographic concepts to tone mapping, including
the
zone system
, which is a way of maintaining consistency from exposure to
print originally developed by photographers Ansel Adams and Fred Archer. In
2003, Helge Seetzen, Lorne A. Whitehead, and Greg Ward published a descrip-
tion of a high dynamic range display device that could display HDR images di-
rectly [Seetzen et al. 03]. An improved version was described in the paper “High
Dynamic Range Display Systems” by the same authors and several others [Seet-
zen et al. 04]. The device uses a low resolution LED grid that acts as a backlight
for a high resolution LCD panel, and is capable of reading and displaying HDR
file formats.
In 2009, the paper “Modeling Human Color Perception under Extended Lu-
minance Levels” by Min H. Kim, Tim Weyrich and Jan Kautz presented a new
model for color perception [Kim et al. 09]. As the title suggests, the model covers
a wide range of brightness levels. The authors conducted psychophysical mea-
surement of human color perception under extended real-world luminance levels.
Based on the analysis of the data, they proposed a new color appearance model
and cast HDR imaging into the model. The results were compelling enough to
remind the CG community of the importance of human color adaptation.
6.1.6 The Effect of Motion-Blur
An interesting ancillary application of HDR imaging is the simulation of mo-
tion blur that results from spinning or moving the camera during the exposure.
The effect is quite simple to create: the image is just filtered in the direction of
the blurring, which Figure 6.5(b) illustrates. The image in part (a) was captured
by actually spinning the camera, part (b) shows the filtering technique applied to
one of the original captured images, and part (c) shows the result of filtering the
actual HDR image. In the absence of high dynamic range data, the filtering cannot
reproduce the light trails of the windows.
6.2 HDR File Formats
Image files for computer graphics traditionally used a three or four channel (RGB
or RGBA) format, with 8 bits per channel. Each color is therefore limited to
