NL Filter NL which stands for non-linear , is an efficient image enhancing filter. Radius is the strength of the filter, and Alpha determines whether the filter will just smooth out, or reduce noise. Recommended values are between 0.0 and 0.5. Optimal estimation smoothing This filter is a bit different from the first, and is very good for reducing dithering noise. Radius should be from 0.8 to 1.0 for this filter to work correctly.
Edge enhancement is the opposite of the smoothing filter.
It sharpens edges instead of blurring them. Radius stands for the effectiveness of the filter. Useful values range somewhere between 0.5 and 0.9. This filter sharpens up your image. You can set the amount of sharpness, and you can get a preview.