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294 Chapter 18: Effects and Environments
Left: The intensity of an IES sun light completely
overexposes a scene.
Right: Logarithmic exposure control correc ts the
overexposure.
Note: Logarithmic Exposure Control is the best
type of exposure control for animations because it
doesn’t use histograms.
Note: You can use the Logarithmic exposure
control with the
mental ray renderer (p age 3–77) .
Note: If you need to use Render To Texture (page
3–139)
, you should not use Automatic or Linear
exposure controls. For the best results, use
Logarithmic exposure control.
See also
Environment Panel (page 3–268)
Inter face
B rightness—Adjusts the brightness of the
converted colors. Range=0 to 200. Default=50.
This parameter is animatable.
Co ntrast—Adjusts the contrast of the converted
colors. Range=0 to 100. Default=50.
This parameter is animatable.
Mid Tones—Adjusts the mid-tone values of
the converted colors. Range=0.01 to 20.0.
Default=1.0.
This parameter is animatable.
Adjusting the value of mid tones
Physical Scale—Sets a physical scale for exposure
cont rol to u se with lights that are not physically
based. The result is an adjust ment of the rendering
that approximates the eye’s response to the scene.
Each standard light’s
Multiplier (page 3–1071)
is multiplied by the Physical Scale value to give
a light intensit y value in candelas. For example,
w ith the default Physical Scale of 1500, a standard
omni lig ht is treated by the renderer and radiosity
as a photometric isotropic li g ht of 1500 candelas.
Physical Scale is also factored into reflections,
refractions, and self-illumination.
Tip: You need to set the Physical Scale w hen you u s e
ray-tracing with self il lumination. Set this value
to the equivalent of the brightest light source in
the scene. This will set the appropriate conve rsion
scale for reflections, self-illumination, and all
other non-physically based elements a material
offers. In some cases, an object might reflect or
emit more light than the brightest li ght object in
the scene; in this case, use the object’s Luminance
value as the Physical Scale.