Hi,
Exactly the same happens here, using Paint.Net 3.36 (Win Vista SP1).
After saving, some of the existing EXIF-values will have changed to strange values, and one item has gone missing.
Example values (before save):
InteroperabilityOffset - 3362
FileSource - DSC - Digital still camera
Macro mode - Normal
Self timer - Off
Quality - Superfine
Easy shooting mode - Manual
Contrast - Normal
Sharpness - High , +1
Metering mode - Evaluative
Focus type - Auto
'Same' values (after save):
InteroperabilityOffset - (no longer present)
FileSource - Other
Macro mode - Macro
Self timer - 16/10 sec
Quality - Normal
Easy shooting mode - Full Auto
Contrast - High , +4
Sharpness - Normal
Metering mode - Center weighted averaging
Focus type - Manual
It so happens to be that my camera is also a Canon Powershot A650 IS, exactly the same as the previous poster. But this shouldn't really matter, should it??
The EXIF values were read from file & copied here using Irfanview 4.23.
I can send you the pictures if needed (original + modified).
Thanks,
Peter