How do I increase the resolution of exported graphs (.tif or .jpg)?

I am using GAUSS 19/20. I would like to export graphics into .tif format, a format often requested by medical journals.   I cannot figure out how to export the graph with sufficient resolution to make it publication quality. Increasing the dpi parameter in plotSave() seems to have no effect.  Any help would be very much appreciated.  In the old graphics, I would convert the graph to the .emf format, then convert that to .tif or .jpg or whatever the journal wanted.  Those converted files had excellent resolution.