Your understanding is correct, sigmaF values aren't required for
calculating electron density.
Many programs that calculate maps have an option to use the F/sigmaF
ratio to threshold the amplitudes used in map calculation - which would
require sigmaF. This isn't something I've seen used recently. The
presence of sigF is also sometimes used as a proxy for confirming that
the data is observed rather than calculated.
Pete
Francisco Hernandez-Guzman wrote:
Hello everyone,
My apologies if this comes as basic, but I wanted to get the expert’s take on
whether or not the sigmaF values are required in the calculation of an electron
density map. If I look at the standard ED equation, sigma’s don’t appear to be
a requirement but all the scripts that I’ve looked at do require sigma values.
I wanted to calculate the electron density for PDB id: 1HFS but the structure
file only lists the Fo’s, Fc’s and Phases, but no sigmas. Would such structure
factor file be considered incomplete?
Thank you for your kind explanation.
Francisco
