how can I copy custom exif fields from one image to another with exiftool?

Question

I am trying to copy all metadata from one image to another, including custom exif fields (in this case absolute and relative altitudes present in images from my DJI drone) using the command:

exiftool -tagsfromfile orig.jpg -all:all new.jpg

however only the standard tags are copied:

exiftool -s orig.jpg | grep -i alt

> GPSAltitudeRef                  : Above Sea Level
> AbsoluteAltitude                : -10.68
> RelativeAltitude                : +60.90
> GPSAltitude                     : 60.9 m Above Sea Level


exiftool -s new.jpg | grep -i alt

> GPSAltitudeRef                  : Above Sea Level
> GPSAltitude                     : 60.9 m Above Sea Level

Is there any way to copy all the tags across automatically, or do I have to add them one at a time?

Thanks for your help

Answer 1

Try:
exiftool -tagsfromfile orig.jpg -exif new.jpg

Edit: See the last few paragraphs of Exiftool FAQ #9. A similar command is mentioned there but unfortunately was inaccurate until today.

Answer 2

As you say, AbsoluteAltitude and RelativeAltitude do not appear to be defined tags. exiftool cannot copy them if it does not know how they are defined. In Phil Harvey's (author of exiftool) answer in this discussion at exiftool's forum, you must create a user-defined tag in order for exiftool to write it.

Please see the exiftool sample config file for details and examples.