Exactly where does Lightroom Classic 7.1 store XMP data?

[mjs9876543210]

Question: When LR Classic says it stores changes in XMP, where exactly is it storing it (i.e. what tags is it using), and why doesn't the file's last written time change?

Background:

I have a catalog with "Automatically write changes into XMP" turned on. It was turned on before I imported anything. I imported the photos and ran facial recognition on them. (All files are JPEG.)

There are two surprising results that have me concerned the facial recognition data (and other data) didn't make it into the files:

• The write date of the file hasn't changed.
• exiftool doesn't show any additional tags.

Perhaps I misunderstand what the "Automatically write changes into XMP" means - my expectation was that everything that would otherwise be stored in LR's database would *also* be stored in the individual image file. But now I'm not so sure.

Thank you for helping me understand this better,

Mike

[Just Shoot Me]

If you have that option turned on it stores it right next to the image file. You will see the image file name with the RAW file extension and right next to it will be another file with the exact same name and a XMP file extension.

[Just Shoot Me]

Sorry I didn't read your complete post before I replied.

JPG, TIFF PSD and I think PNG files have a special section, in the file itself, to store XMP data without creating a second file.

Facial recognition might not be stored in XMP, for RAW image files, or inside a JPG file. It might only be stored in the catalog file itself.

Not everything is stored in a XMP file or written into the file itself with JPG's.

[DdeGannes]

Lightroom by default stores all medata and edits you do in the Lightroom Catalog file. As you are aware you can select the option to automatically write to xmp this function will write metadata out to xmp files. However functions that are specifically applicable to Lightroom and are not utilized by Adobe Camera Raw do not get written out e.g History steps, Collections, Smart Collections, Virtual copies,etc,etc,etc! You can do a web search to obtain a full list.

When Lightroom functions it is reading and writing from the Catalog file by default.

[mjs9876543210]

Thank you for your help.

We really are captive to the vendor, apparently no matter which tool we choose. 😞

[JP Hess]

What do you mean by that? What is it that you are looking for?

[mjs9876543210]

I was trying to figure out exactly which tags LR Classic uses to store, in this example, facial recognition metadata. From what I can tell, and informed in part by the earlier replies, apparently LR does not store all metadata in tags (or sidecar files).

If the metadata actually were stored in documented (or at least discoverable) tag structures then there'd be some hope of being able to migrate that metadata to new tools. But since it's buried in the catalog in, from what I can tell, a completely opaque way there's no way I can see to migrate that data, manipulate it, etc.

I assumed that with the  "Automatically write changes into XMP" option turned on, or with its manual equivalent *all* changes would be written. But I now believe I was mistaken.

In contrast, and for example, Picasa (optionally) stores its facial recognition metadata in well known and semi-standard tags.

[johnrellis · Accepted solution]

LR stores everything shown in the Metadata panel, Keywords panel, and face recognition is stored in industry-standard metadata fields in the photo. The face recognition metadata is stored according to the Metadata Working Group's standard, e.g.

$ exiftool -a -G Photo_061505_002_edited-1-2-2.jpg | grep -i region
[XMP]           Region Applied To Dimensions W  : 640
[XMP]           Region Applied To Dimensions H  : 480
[XMP]           Region Applied To Dimensions Unit: pixel
[XMP]           Region Rotation                 : 0.16017, 0.00000
[XMP]           Region Name                     : Peter
[XMP]           Region Type                     : Face, Face
[XMP]           Region Area H                   : 0.32505, 0.56974
[XMP]           Region Area W                   : 0.24378, 0.40071
[XMP]           Region Area X                   : 0.74400, 0.35106
[XMP]           Region Area Y                   : 0.48796, 0.35815

Normally with "Automatically write changes into XMP" enabled, metadata changes are written back to the file nearly instantaneously, unless you've made large batch changes, which can take several seconds or even longer, depending on how many photos were changed.

If you're not seeing changes getting written back to the file, as a troubleshooting step, try saving manually with Metadata > Save Metadata To File.

[mjs9876543210]

John -

You are correct. The tags are stored as you said. Either I wasn't using exiftool the right way or the metadata was being written asynchronously and it's now caught up. (I'm reasonably sure it's written asynchronously because even if I screwed up the exiftool command I'm essentially certain I didn't screw up the ls command, and the file write timestamp wasn't changed.)

Thank you for setting me straight on this,

Mike