Logarithmic Exposure Control

Environment Dialog

Brightness—Adjusts the brightness of the converted colors. Range=0 to 200. Default=50.

This parameter is animatable.

Contrast—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 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 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.

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 lightbulb 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 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.

Color correction can remove the color “cast” that comes from a light source.

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.

Desaturate Low Levels simulates the eye's response to dim lighting. In dim lighting, the eye does not perceive colors and sees tones of gray instead.

The effect of this setting is not apparent except 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).

Affect Indirect Only—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 scanline renderer. When you use standard lights but leave Affect Indirect Only off, radiosity and exposure control yield results that can be quite different from the default scanline renderer.

In general, you don’t need to turn on Affect Indirect Only when the primary lighting for your scene comes from photometric lights.

Exterior daylight—When on, converts colors for an outdoor scene. Default=off.

The exterior daylight setting compensates for the extreme intensity of an IES sun light.