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Tests with Rating for JPEG files
Start with clean JPEG
Test with FRV
Set Rating in FRV to 2 - XMP file gets created with Rating of 2 written - original file not touched
Open JPEG in Adobe Bridge - no rating detected - presumably because Bridge never expects to read from XMP for a non-RAW file
Open JPEG in PL5 - no rating detected - presumably because PL5 never expects to read from XMP for a non-RAW file
Rating in JPEG has not been changed - delete XMP file as irrelevant and don’t use FRV to rate JPEGs
Using PL5 for JPEG files
Set Rating on JPEG file in PL5 to 3
- Rating of 3 written to JPEG file, both to
exif:ratingandxmp:ratingtags - this is wrong, onlyxmp:ratingshould be written - DOP file created with Rating of 3 written
- XMP file still contains Rating of 2 - presumably because PL5 never expects to write to XMP for a non-RAW file
- nothing written to database
Close PL5, delete DOP file and database
Reopen PL5
- Rating is correctly read from JPEG file
- database is updated from JPEG file - thus proving that it never needed to be written to the DOP file
Conclusion
Apart from unnecessarily writing Rating to the legacy exif:rating tag, PL5 handles the Rating of JPEG files better in that it, at least, writes it directly to the JPEG file, thus preventing data loss in the event of DOP file and database loss. It also means that any other app, including PL4, can read the Rating
Interaction between PL4 and PL5 for JPEG files
Use ExifTool to set Rating of JPEG to 5
Open JPEG in PL4 - Rating of 5 is correctly shown
Change Rating to 3 in PL4 and close PL4
- DOP file is created and contains a Rank of 3
Close PL4 and open JPEG in PL5
- Rating is shown as 5
- DOP file still contains a Rank of 3
Make an image edit to the JPEG in PL5
- DOP file now shows a Rating of 5 and the Rank of 3 has been deleted
Reopen PL4
- even though I have changed the Rating in PL5, PL4 continues to read the Rating of 3 that it wrote and which is still in the PL4 database - presumably because the DOP file no longer contains the Rank.
If I then close PL4, delete its database and reopen it, PL4 then shows the Rating of 5 that PL5 wrote to the JPEG file.
N.B. PL4 only writes and reads Rating from either the DOP file or the database. Delete both of these and all record of Rating is lost.
I remain convinced that reading a JPEG file that has a PL4 DOP, in PL5, should instantly provoke:
- The writing of the Rank found in the PL4 DOP to the JPEG file
- The DOP should then be updated to remove the Rank
- The Rating should not be written to the DOP because it is totally unnecessary and will not be used from then on.