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290 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 standard lights (rather than photometric
lights), u se t he L ogar ithm ic Exposure Control
andturnonAffectIndirectOnly.
• Use Automatic Exposure Control for rendering
still images. Automatic Expo sure Control is
also good for first-draft renderings.
• Use Logarithmic Exposure Control for
animations with a moving camera. (Automatic
and Linear Exposure Control w ith a moving
camera can cause excessive flickering.)
•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, because lig ht intensities don’t vary greatly
across the scene. In this situation, adjusting light
values might be all you need to do to get a good
rendering.
When lig hts 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 range of the (simulated) physical
scene, into the smaller dy namic range of the
display.
Interfa ce
Drop-down list—Choose which exposure control
to use.
Active—When on, the exp osure control is used in
renderings . When off, the exposure control is not
used.
Process B a ckgr ound a nd Envir onment M aps —When
on, the scene background and environment maps
are subjected to exposure control. When off, they
are not.
Preview t humbnail—The thumbnail displays a
preview of the rendered scene with the ac tive
exposure control applied. Once a preview has
been rendered, it updates interactively w hen you
changed exposure control settings.
Render Preview—Click to render the preview
thumbnail.