Ribbet does not accept all RAW image files.
RAW is a non-standard image file format that some camera manufacturers (Canon, Nikon, etc.) provide for more advanced cameras. As each version of RAW from each manufacturer is a little different, there are too many different versions out there for us to support them all successfully. Until manufacturers agree on a standard format we can’t keep up with all of them, however many RAW formats are already supported by Ribbet.