[phenixbb] difference map based on the cryo-EM map

Dear All, Supposed  by phenix.real_space_refine I got a PDB of protein-ligand, will you please let me know how to get the subtraction map (difference map?) which only show the density of the ligand, so that I can see whether the ligand was well resolved in the map, or whether the built ligand fits well with the ligand density? Smith