Vielen Dank, Andre, but I don't seem to correctly understand you.
As far as I understand you, you recommend to clear the "cpg14x_exif" table. However, if I am able to handle my phpMyAdmin correctly, it seems to me, that in this table only the specifications laid out in cpg's "EXIF Manager" are stored, i.e. which exif fields are of interest and should be displayed -- I can't find the data in it, that is displayed in the file information area under the picture. In cpg's exif manager I already changed which tags I'd like to have additionally displayed.
I then uploaded one test image, in which I deleted EXIF data AND keywords. However, still the old information is displayed. And I also upload a file in which more keywords were present. No change in the displayed information....
As for the keywords, I suppose that those are stored in the field "keywords" within the "cpg14x_pictures" table. At least cpg displays these keywords (which corresponded to the keywords in the "old" jpgs iptc data), and not the keywords in the iptc tag now present on the server.
So, once again: I suppose cpg displays the file information data (i.e. exif AND keywords) out of some of its sql tables. I suppose that the data was written into those tables when the files were batch-added to the database for the first time. And if I want the displayed information to reflect the "new" information in the new tags of the new jpgs (which of course still have the same filename), I will need coppermine to update the relevant tables. But I don't know how to do this....