9

Logarithmic Exposure Control 299
terms of its effect on reflections and refractions.
Physical Scale does affect the appearance of
self-illuminated materials.
Range=0.0 to 200,000.0 candelas. Default=1500.0.
Asinglecandleisapproximately1candela(the
unit can also b e cal led a "candle"). A 100-Watt
(W) incandescent light bulb is approximately
139 c andelas (cd). A 60W bulb emitting in all
directions is about 70 cd, while the same bulb with
a reflector is about 4500 cd because the light flux is
concentrated into a narrow angle.
Photometric lights are unaffected by the Physical
Scale value.
This parameter is animatable.
Color Correction check box and color swatch—When
the check box is turned on, color correction shifts
all colors so the color displayed in the color swatch
appearsaswhite.Default=off.
Clicking the color swa tch displays a Color Selector
(page 1–161) so you can choose the color to adapt
to.
You can use this control to simulate how the
eye adjusts to lighting. For example, even when
the light in a room has a yellow hue from an
incandescent light bulb, we will continue to
perceiveobjectsthatweknowtobewhite,suchas
printed pages, as white.
Tip: For t he best results, use a very pale color
correctioncolor,suchasapaleblueorpaleyellow.
Color correction can remove the color “cast” that com es from
a light source.
Desaturate Low Levels—When on, renders dimly
lit colors as if the light were too dim for the eye
to d istinguish between colors. When off, renders
even dimly lit colors. Default=off.
Desaturate Low Levels simulates the eye’s response
to dim lighting. In dim lighting, the eye does not
perceive colors and sees tones of gra y instead.
Theeffectofthissettingisnotapparentexcept
at very low light levels, below 5.62 footcandles
(lumens per square foot). When the illuminance
is less than 0.00562 footcandles, the scene is
completely gray.
Note: 1 footcandle (fc) equals 10.76 lux (lumens
per square meter).
Af f e ct I nd i rect O n l y —When on, Logarithmic
Exposure control is applied only to areas of
indirect lighting. Default=off.
Turn on this toggle when the primary lighting for
your scene comes from standard lights rather than
photometric lights. When you use standard lights
and turn on Affect Indirect Only, radiosity and
exposure control yield results similar to the default