It can be educational (even useful at lower resolutions) to sharpen or blur a map. This can be achieved with the sharpening tool Calculate -> Map Sharpening.... By default, the maximum and minimum sharpness is +/- 30Å^2, this can be changed (in this case to 80) using:
(set-map-sharpening-scale-limit 80)
This currently only works on maps created by reading an MTZ (or other) reflection data file.