Can’t empty field

[PatrickMarq]

For some strange reason I can't remove a value, probably me 

My film workflow in compleet in Lightroom with Negative Lab Pro who uses exiftool somewhere in the background.
I convert my scan from negative to positive with NLP after that I use NLP to create a positive tif image.

But then in the caption I have this line:
Digitized with Negative Lab Pro v2.1.2

If I set the value to iptc:Caption-Abstract="." The text is gone but there is a period not so clean.
If I try -iptc:Caption-Abstract= the text remains.

[StarGeek]

Run the command listed in FAQ #3 to see if the same data is elsewhere in the file.  I'm guessing that it also appears in the XMP:Description tag.  Maybe EXIF:ImageDescription as well.

I believe Lightroom follows the Metadata Working Group specification for dealing with metadata so it will often write a value to two or more actual tags to have the most compatibility with other software.