You can use the sharpening filters on grayscale images to make differences in shading more distinct.
Sharpening filters can enhance edges in the image. It may be necessary to use these filters to extract the highest amount of useful data from a low resolution scan.
For more information on the two types of sharpening filters, see Highpass Filters and Edge Enhancements Filters.
AutoCAD Raster Design toolset uses Single Image Optimization to speed up the editing commands.