Thank you for the information. So I'm I out of luck if I have Windows Vista???
In that case, download the free DNG converter version 9 (you may already have it)
Use the DNG converter to convert all RX100M3 Raw files to DNG format then edit the DNGs (not the Raw files) in Elements 12.
Are you sure that DNG Converter 9.0 will run on Vista - the system requirements says only Windows 7 or 8.1.
The last DNG Converter to run on XP/Vista is 8.3 and that doesn't support the DSC-RX100 III.