2008

Physical Scale Sets a physical scale for exposure control to use with lights
that are not physically based. The result is an adjustment of the rendering
that approximates the eye's response to the scene.
Each standard light's
Multiplier on page 7859 is multiplied by the Physical Scale
value to give a light intensity value in candelas. For example, with the default
Physical Scale of 1500, a standard omni light is treated by the renderer and
radiosity as a photometric isotropic light of 1500 candelas. Physical Scale is
also factored into reflections, refractions, and self-illumination.
TIP You need to set the Physical Scale when you use ray-tracing with self
illumination. Set this value to the equivalent of the brightest light source in the
scene. This will set the appropriate conversion 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 light object in the scene;
in this case, use the object's Luminance value as the Physical Scale.
Range=0.0 to 200,000.0 candelas. Default=1500.0.
A single candle is approximately 1 candela (the unit can also be called a
"candle"). A 100-Watt (W) incandescent light bulb is approximately 139
candelas (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
appears as white. Default=off.
Clicking the color swatch displays a
Color Selector on page 331 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 perceive objects that we know to be white,
such as printed pages, as white.
TIP For the best results, use a very pale color correction color, such as a pale blue
or pale yellow.
Desaturate Low Levels When on, renders dimly lit colors as if the light were
too dim for the eye to distinguish between colors. When on, renders even
dimly lit colors. Default=off.
Exposure Controls | 6539