As Frank said OpenEXR output (chosen from the drop-down list on the Save dialog) allows for full 32bit/channel HDR image output in a standard, widely compatible format. However in some cases banding can still occur. Sometimes this is due to reducing sample jitter, as Frank mentioned, but in other cases there is simply too smooth a gradient in the sky and it is your display device, not the image, that is showing banding. This is particularly true of LCD's which generally cannot display as wide a color range as CRT's. We may implement some form of dithering in 8bit image output to counteract this in this in the future.
- Oshyan