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294 Chapter 18: Effects and Environments
Left: Linear exposure control maps intensity evenly.
Right: Logarithmic exposure control maps most intensities to
low and mid tones.
Tips:
• If the primary lighting from your scene comes
from st andard lights (rather t han photometr ic
lights), use t he L ogarithmic Exposure Control
andturnonAffectIndirectOnly.
• Use Automatic Exposure Control for rendering
still images. Autom atic Exposure Control is
also good for first-draft renderings.
• Use Logarithmic Exposure Control for
animations with a moving camera. (Automatic
and Linear Exposure Control with a moving
camera can cause excessive flicke ring.)
•ForoutdoorscenesthatusetheDaylight
system, turn on the Exterior toggle to prevent
overexposure.
Exposure and Attenuation for Standard
Lights
When you use standard lights that are not
attenuated, renderings tend to have a low dynamic
range, b e cause light intensities don’t vary g reatly
across the scene. In this situation, adjusting light
values might be all you need to do to get a good
rendering.
When lights are attenuated, on the other hand, the
light might be too bright on near surfaces or too
dim on far surfaces. In this situat ion, Automatic
Exposure Control can help, because it adjusts the
larger dynamic r ange of the (simulated) physical
scene, into the smaller dynamic range of the
display.
Interfa ce
Drop-down list—Choose w hich exposure control
to use.
Active—When on, the exposure control is used in
renderings . When off, the exposure control is not
used.
Process B ack ground and Envir onment M aps —When
on, the scene background and environment maps
are subjected to exposure control. When off, they
are n ot.
Preview thumbnail—The t humbnail displays a
preview of the rendered scene with the active
exposure control applied. Once a preview has
been rendered, it updates interactively when you
changed exposure control settings.
Render Preview—Click to render the preview
thumbnail.