Electron Density Contour Levels

[Andrew Orry]

Q.

 I have a question about the contour level, there seems to be two default levels {1, 2.5}, is the "1" for 2mFo-Fc and the "2.5" for mFo-Fc, or both 1 and 2.5 is for 2mFo-Fc level?

A.

Two contour levels at 1 and 2.5 sigma respectively are generated for the 2Fo - Fc  map.  The levels are arguments to a macro and can be changed when you contour in the Tools/X-Ray/Contour Electron Density. They also can be interactively changed by pressing on + and -  in the workspace on 'graphical objects'/meshes representing the contours.