This is a bit tricky, so I'm not surprised you are having problems.

Writing "MakerNotes:All" writes the individual makernotes values, but the makernotes IFD (the block of MakerNotes information) is itself not a MakerNotes tag because it is written to the ExifIFD, not the MakerNotes IFD. (I hope this makes sense.) So if you want to write just the maker notes, you have to write that single ExifIFD tag.

Another complication is that this tag is named differently for each manufacturer (see the EXIF Tags documentation). So in your case you need to write "MakerNoteCanon".

To further complicate things, this won't work for a general image because in order to identify the maker notes as being "MakerNoteCanon", the Make and Model must be set correctly in the destination image. So to be sure this is right, you should also copy the Make and Model tags unless you know they are already correct. ie)

(Notice that I didn't need to use "-makernotecanon>makernotecanon" because the ">TAG" is only necessary if you are redirecting the tag information to a tag of a different name.)

This should do what you want. Let me know if any of this is unclear.

- Phil