Rendering menu > Environment > Environment and Effects dialog > Environment panel > Exposure Control rollout
Exposure Controls are plug-in components that adjust the output levels and color range of a rendering, as if you were adjusting film exposure. Exposure Controls are especially useful for renderings that use radiosity.
Exposure control compensates for the limited dynamic range of monitors. Monitors have a dynamic range of about two orders of magnitude. The brightest color that appears on a display is about 100 times brighter than the dimmest. The eye, by comparison, can perceive a dynamic range of about 16 orders of magnitude. The brightest color we can perceive is about 10 million-billion times brighter than the dimmest. Exposure control adjusts colors so they better simulate the eye's great dynamic range, while still fitting within the color range that can be rendered.
-
Automatic Exposure Control samples the rendered image and builds a histogram to give good color separation across the entire dynamic range of the rendering. It can enhance some lighting effects that would otherwise be too dim to see.
-
Linear Exposure Control samples the rendering and uses the average brightness of the scene to map physical values to RGB values. Linear Exposure Control is best for scenes with a fairly low dynamic range.
-
Logarithmic Exposure Control uses brightness, contrast, and whether the scene is outdoors in daylight to map physical values to RGB values. Logarithmic Exposure Control is better for scenes with a very high dynamic range.
-
Pseudo Color Exposure Control is actually a lighting analysis tool. It maps luminances to pseudo colors that show the brightness of the values being converted.
Important: The mental ray renderer supports only the Logarithmic and Pseudo Color exposure controls.
-
If the primary lighting from your scene comes from standard lights (rather than photometric lights), use the Logarithmic Exposure Control and turn on Affect Indirect Only.
-
Use Automatic Exposure Control for rendering still images. Automatic Exposure Control is also good for first-draft renderings.
-
Use Logarithmic Exposure Control for animations with a moving camera. (Automatic and Linear Exposure Control with a moving camera can cause excessive flickering.)
-
For outdoor scenes that use the Daylight system, turn on the Exterior toggle to prevent overexposure.
When you use standard lights that are not attenuated, renderings tend to have a low dynamic range, because light 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 lights are attenuated, on the other hand, the light might be too bright on near surfaces or too dim on far surfaces. In this situation, Automatic Exposure Control can help, because it adjusts the larger dynamic range of the (simulated) physical scene, into the smaller dynamic range of the display.
Drop-down list—Choose which exposure control to use.
Active—When on, the exposure control is used in renderings. When off, the exposure control is not used.
Process Background and Environment Maps—When on, the scene background and environment maps are subjected to exposure control. When off, they are not.
Preview thumbnail—The thumbnail displays a preview of the rendered scene with the active exposure control applied. Once a preview has been rendered, it updates interactively when you changed exposure control settings.