Setting lens make, model and name from XMP

[monochrome]

I have a bunch of movie files. Each movie file stores some metadata in an XMP sidecar file, and that metadata is loaded and displayed fine in IMatch. With one exception: I can't make the lens name display in the camera dashboard.

I understand that IMatch uses the tag photools.com::IMatch\2900\lens\0 to keep track of the evaluated, normalized lens name, which is derived from a number of other tags. What I wonder is:

1. Is there a way to set some value in the XMP that will set the value of that tag with no further matching or testing? For example, I could set ExifAUX "Lens" XMP tag and just have IMatch use that value right as-is. Or the ExifEx Lens Make and Lens Model tags. Some way of saying to IMatch "Ok, this is the name of the lens. I know it. Just use it."

2. Where does the Camera dashboard get its lens name from? I have files where no lens name is shown, but where the photools.com::IMatch\2900\lens\0 is populated. (All of these are movie files, and they have no LensID, just a LensSpec tag from Exiftool. For example, the "Sigma 10-20mm F4-5.6 EX DC HSM" is listed as "10-20mm f/4-5.6 G".)

[Mario]

Where does the XMP with your lens name come from?

Lens is yet another bad example for how camera vendors fu*k up metadata.
Not all camera vendors fill out the official EXIF lens data.
Some camera vendors (Nikon!) encrypt the lens data.
There is no relation between the lens number embedded in EXIF and a specific lens model.
Different camera vendors use the same ids, the same camera vendor uses the same ids for different lenses.
They just don't care and their paying users let them get away with it...

Phil Harvey maintains a huge list of lens names and more or less complex ways to figure them out from a wide range of EXIF tags and maker notes.
This list is always extended, incorporating the lens information supplied to him by users (hint, hint).

If camera vendors would just recognize than it is now 2017 and not 1997 and get rid of EXIF in favor of XMP, they could just store the fully-qualified lens name in the XMP - and this would be good for all users. But users have no lobby, they just pay for all that stuff.

In addition to the heroic efforts ExifTool does to come up with a more or less sensible and accurate lens name, IMatch maintains a meta-tag on top of the various lens tags provided by ExifTool. Again, an effort to come up with a usable lens name across a wide variety of file formats. And yes, I'm pi**ed of by all this nonsense the camera vendors cook up. I always wonder why the sh*t hits my fan all the time, and users don't just go to their camera vendors and demand clean and proper metadata - YOU PAY for all this, in the end.

The photools.com lens tag is field from these tags:

Composite\LensID\LensID
Exif::Main\42036\LensModel
Exif::Main\42034\LensInfo
Composite\LensID-4\LensID
Composite\LensID-3\LensID
Composite\LensID-2\LensID
Composite\LensSpec\LensSpec

Top to bottom, best hit counts.
The Composite tag is filled by ExifTool from different pieces of information. The lens is 23 can mean dozens of different models, depending on the camera, lens id, 10 other EXIF tags, firmware versions and the moon phase.