To adjust exposure
- Click Render tab
System panel Autodesk Rendering 
. - Click the Environments tab, and go to the Exposure panel.
- Use Exposure Value slider to control overall brightness of the rendered image. This setting is comparable to the exposure compensation setting in cameras with automatic exposure. You can set a value between -6 (brighter) and 16 (darker). The default value is 6.
- Use the Highlights slider to adjust the light level for the brightest area of the image. You can set a value between 0 (darker highlights) and 1 (brighter highlights). The default is 0.25.
- Use the Midtones slider to adjust the light level for areas of the image whose brightness lies between the highlights and the shadows. You can set a value between 0.1 (darker mid tones) and 4 (brighter mid tones). The default is 1.
- Use the Shadows slider to adjust the light levels for the darkest areas of the image. You can set a value between 0.1 (lighter shadows) and 4 (darker shadows). The default is 0.2.
- Use the White Point slider to control color temperature of the light sources that should display as white in the rendered image. This setting is similar to the White Balance setting on digital cameras. The default value is 6500.
If the rendered image looks too orange, reduce the White Point value. If the rendered image looks too blue, increase the White Point value.
- Use the Saturation slider to modify intensity of colors in the rendered image. You can st a value between 0 (gray/black/white) and 5 (more intense colors). The default is 1.
Be sure to select the On check box to turn the exposure on. The effects will be visible for both realistic and photorealistic visual styles.