2008

Exposure controls are plug-in components that adjust the output levels and
color range of a rendering, as if you were adjusting film exposure. This process
is known as tone mapping. These controls are especially useful for renderings
that use
radiosity on page 5976 , and when dealing with high-dynamic-range
(HDR) imagery.
Exposure control compensates for the limited dynamic range of monitors.
Monitors have a dynamic range of about two orders of magnitude. The
brightest color that appears on a display is about 100 times brighter than the
dimmest. The eye, by comparison, can perceive a dynamic range of about 16
orders of magnitude. The brightest color we can perceive is about 10
million-billion times brighter than the dimmest. Exposure control adjusts
colors so they better simulate the eye's great dynamic range, while still fitting
within the color range that can be rendered.
The exposure controls included with 3ds Max are:
■
Automatic Exposure Control on page 6534 samples the rendered image and
builds a histogram to give good color separation across the entire dynamic
range of the rendering. It can enhance some lighting effects that would
otherwise be too dim to see.
■
Linear Exposure Control on page 6537 samples the rendering and uses the
average brightness of the scene to map physical values to RGB values.
Linear Exposure Control is best for scenes with a fairly low dynamic range.
■
Logarithmic Exposure Control on page 6540 uses brightness, contrast, and
whether the scene is outdoors in daylight to map physical values to RGB
values. Logarithmic Exposure Control is better for scenes with a very high
dynamic range.
■
mr Photographic Exposure Control on page 6544 gives you
camera-like controls including shutter speed, aperture, and film speed, as
well as image control over highlights, midtones, and shadows.
■ Pseudo Color Exposure Control on page 6552 is actually a lighting analysis
tool. It maps luminances to pseudo colors that show the brightness of the
values being converted.
IMPORTANT The mental ray renderer on page 6039 supports only the Logarithmic,
mr Photographic, and Pseudo Color exposure controls.
6532 | Chapter 19 Effects and Environments