What is xmp

davebmck · Apr 22, 2008

I did a search on this and didn't find anything, so I will ask here. When I look through my file folders where my raw and jpg files are stored I see that some files have the same name with an xmp extension. Some do not have the mating file.

The questions is, what is this file and do I need to keep it?

EricBrian · Apr 22, 2008

Extensible Metadata Platform
http://en.wikipedia.org/wiki/Extensible_Metadata_Platform

davebmck · Apr 22, 2008

OK, that's a technical explanation, but it seems that it is some type of meta file that would be embedded in a document or file. That doesn't tell me what the specific file associated with my picture file contains and whether I need to keep it. Does it contain the modifications I have made to a raw file, or something like that?

crh428 · Apr 23, 2008

That wiki page said it was a metadata file, so I clicked on metadata to find out what the hell that was...

http://en.wikipedia.org/wiki/Metadata

I would say keep it, I doubt it takes up that much space...

PNA · Apr 23, 2008

From what I gather, it's a file created when you make changes in "camera raw" before opening it in PS. If you open the raw file directly into PS w/o touching it in camera raw, there is no file created......my experience.

davebmck · Apr 23, 2008

More recently, I have been converting my raw files to DNG format when I download them. The dng files do not have the xmp files associated with them.

Garbz · Apr 24, 2008

Quick explanation. These files are used where changes are made to an image but the image isn't updated. The changes are recorded in xmp files on the side. Cases where this happens if you have any RAW file opened in a RAW editor. Any changes made in that editor are saved along side the file, because either the editor does not want to or is infact unable to edit the original file. Lightroom and Bridge both do this and it's a great idea if you want to cancel any changes you make later on.

The reason this does not happen with DNG is because the DNG format allows for this information to be embedded. DNG is a container format designed to contain an uncompressed RAW, a compressed RAW, or both, in a specific format, and if selected the original format can be embedded along side, a small, medium, and large preview image, metadata, and the extended changes.

With DNG the info is embedded in the file still with no changes made to the original.

PNA · Apr 24, 2008

Thanks, Garbz.....that's a good explanation!

davebmck · Apr 24, 2008

Garbz said:
Quick explanation. These files are used where changes are made to an image but the image isn't updated. The changes are recorded in xmp files on the side. Cases where this happens if you have any RAW file opened in a RAW editor. Any changes made in that editor are saved along side the file, because either the editor does not want to or is infact unable to edit the original file. Lightroom and Bridge both do this and it's a great idea if you want to cancel any changes you make later on.

The reason this does not happen with DNG is because the DNG format allows for this information to be embedded. DNG is a container format designed to contain an uncompressed RAW, a compressed RAW, or both, in a specific format, and if selected the original format can be embedded along side, a small, medium, and large preview image, metadata, and the extended changes.

With DNG the info is embedded in the file still with no changes made to the original.

Excellent explanation. Let's see if I understand this correctly. The xmp file contains information where I have made changes to a raw file and did not save the changes. Is that correct? For example, if I open a raw image make a few changes to test how something works, and then hit Cancel instead of Done, Save Image or Open Image, the raw file will be unchanged, but the changes would be saved in the xmp file. Is that right?

If that is so, that would explain why some of my modified raw files do not have an xmp file associated with them while some do. It would also mean that I can delete them without concern.

davebmck · May 5, 2008

I thought I would update this thread as I found my last post was incorrect. I took a modified raw file that I had once edited and was planning to delete. I first deleted the xmp file and then reopened the raw file to see if there would be any changes. What I found is that all the previous changes were gone. The raw file was back to its "as shot" state. So don't delete your xmp files if you want to save the changes you have made to your raw files.

Garbz · May 6, 2008

Yes sorry I missed the last post. It's not that the changes won't be saved, it's that the changes can't be saved. RAW is a proprietary format that holds only the sensor data and the camera settings.

If you cancel, or right click and reset your development settings the xmp will be gone again, or very small.

And DNG completely omits the need since the format can store both the original raw file and the additional information that's now in the xmps.