may be a missing tag into Exiftool db

[mahikeulbody]

When I do exiftool -G1 -j file.jpg (see attached file) I get 'IFD1:XResolution' and 'IFD1:YResolution' tags which are not known in the Exiftool db such as provided by exiftool -listx -s -f. I have a Canon S95 camera. They are maybe some others IFD1 tags with this problem*.

NB. I get also 'IFD0:Xresolution' and 'IFD0:YResolution' which are known in the db.

Edit: There are also the following tags:
IFD1:ResolutionUnit
IFD1:Compression

[Phil Harvey]

The ExifTool database doesn't list all of the possible locations of the EXIF tags.  In TIFF images, most of these tags may exist in any IFD# or SubIFD# (where # is any number).  The family 1 group listed in the database for EXIF tags is only the common location.

- Phil

[mahikeulbody]

Thank for the answer.

I fail to understand why a camera maker decides to put the same information within two different fields of the same file...

[Phil Harvey]

For some things this makes sense (ie. the thumbnail resolution is different than the main image), but for other things it doesn't (some Sony cameras write the Model to both IFD0 and IFD1, which is just weird).

- Phil