I have carried out MD simulations on a set of proteins belonging to a protein family. Further, I computed the water density around the protein and have the output in .dx format. I want to use Chimera to visualize the water density around the protein within 4  A.

For this, I loaded the protein and the .dx file in volume viewer, selecting the protein and changing the zone to 4 and generating results.  I want to have a comparison of water density across all proteins. I am unable to understand how to normalise the settings so that the results are comparable.  What I understand is to keep the step same. Additionally,  all the .dx files have different ranges which is obvious, what should be the value of level so that I can compare the water density across  different proteins? Should it be kept at a median value of the range or something else? Please help. If I keep everything default, the results are misleading.