Hi I have a question about solvent mask in cctbx. I generated a mask using the mask manager. Then I am calculating the structure factors from the mask (using mask_manager.structure_factors() ). If I am trying to redo a map from the calculated structure factors (outside the cctbx and I hope without any scaling), I get a map with a mean density of zero, which is not the case of the original mask. I suppose that the structure_factors() function is doing some scaling at some point. In the source codes of the function structure_factors , I found scale = miller_set.unit_cell().volume() / matrix.col(fft_manager.n_real()).product() map_of_coeff *= scale from_map = maptbx.structure_factors.from_map( miller_set.space_group(), anomalous_flag, miller_set.indices(), map_of_coeff, conjugate_flag) But I don't understand what the "scale line" is doing. So I wonder what is exactly this matrix.col(fft_manager.n_real()).product() doing? And how do I generate structure factors for a mask without any scaling? Thanks for any help Celine