Select the appropriate image quality level for the original and scan at the optimal level of image quality.
For details, refer to Here.
Select the scan density (dark, light) of the original.
For details, refer to Here.
You can adjust the density of the background area for originals with colored backgrounds (newspaper, recycled paper, etc.) or originals that are so thin that text or images on the back would be scanned.
For details, refer to Here.