As you know, Canon EOS 7D (for example) raw file contains two LensType tags inside Makernotes (older cameras had one tag only).
If I modify this tag(s):
exiftool -n -canon:lenstype=150 myfile.cr2
-i get expected result (both of two tags are changed).
But, if I wish to set this tag to "Unknown(-1)" lens:
exiftool -n -canon:lenstype=-1 myfile.cr2
-then only one tag (22dec) is changed to -1, while another (239dec) doesn't change.
Any idea? Thanks for answering.