Unrecognized MakerNotes Only Shown When Tag not Found

[mulu]

I am doing a

exiftool.exe -XMP-iptcExt:PersonInImage [Filename]

Many of my images will display "Warning: [minor] Unrecognized MakerNotes" however ONLY when there is no PersonInImage tag in the meta data. When this tag is available then I never see this warning.

Now for the images where the PersonInImage tag is present I add another tag. So when adding that tag I get the "Warning: [minor] Unrecognized MakerNotes". Note that his is for images that did not show this warning when reading the PersonInImage tag.

So
1) Why is this warning never shown when the tag PersonInImage exists?
2) And why is that warning showing up when I write another tag to that same file that previously didn't show that warning when reading the PersonInImage tag?

[Phil Harvey]

ExifTool will show the warning as a hint if nothing is extracted during a read command.  But if you got what you want, then the warning isn't displayed unless you specifically request the -warning tag.  To see all warnings, do this:

exiftool -validate -warning -a FILE

- Phil

[mulu]

Phil, thanks. That explains what I am seeing.