Setting GPS coordinates blanking out exif 'image description' field

[Gary D.]

Hi
I use vuescan to scan negatives and use the description field to save information about the roll of film.
VUESCAN puts that information into the EXIF field 'Image Description'
I then use Photomechanic to add other meta data using a template.  The template will copy the {description} variable into the  XMP caption and job ID.
I'll then add GPS coordinates,
Then apply  keywords
and then pick the images that get passed on to lightroom for editing.

I changed my workflow to set the GPS coordinates first ( so I could let PM fill in the event location fields.)
If I set the GPS coordinates BEFORE  I apply the template.. the  exif 'Image Description' Field is deleted, and when I apply the template there is no value in the variable {description} so the caption and job id are blank.
If I apply the template first and then set the GPS coordinates the exif 'image description' is left alone.

Here are the steps I take


Scan negative using VUESCAN  to a TIF file, add text to description ( exif  image description field)
Go to PM and select all images

Open Image Metadata template,  Clear template, Load template GDD_NewScan.XMP,  Add information to headline,  apply template to all selected
Open Image-> Set GPS Coordinates,  find location, accept, apply to all
Open Metadata Template, clear, Set the event location fields to get location from geotag, apply template to all selected
do keywords
select images for Lightroom...

This works fine  exif 'image description' is still set.  (verified by using exiftools to dump all the metadata

TEST2
Scan negative using VUESCAN  add text to description ( exif  image description field)
Go to PM select all images
Open Image -> Set GPS Coordinates, find locatoin, accept, apply to all

The exif image description field is blank
Open Metadata template,  Clear template, Load template GDD_NewScan.XMP,  Add information to headline,  set event location fields to get location from geotag, apply template to all selected

and since the image description is blank the   caption and job id are blank.

Im using PM6.0, build 3558 (afa5073)
on an iMac running macOS 10.14.6
I've attached the template I use, the original file from Vuescan , the file after geotagging and the meta data dumps from exiftools.

Gary

[Hayo Baan]

I took a look at the files and indeed, after setting the GPS coordinates, the ImageDescription is gone. I did some further research and I found that if you set the caption, it overrides the ImageDescription field with the new caption.

So the problem, I think, we have here is that PM does not consider the EXIF ImageDescription as a source for the caption, but does write to it when updating/setting the caption information. This sounds like a bug, or at least unwanted behaviour.