XMP Sidecar Files - Part 2

by Michael Clark

In my last blog post about XMP sidecar files and Lightroom, there were quite a few comments and questions. In the course of answering some of those questions, I realized that there are a few tricks to using the XMP files so that you can transfer images from one computer to another and have all of your develop and metadata settings in Lightroom retained between machines.

The key to all of this is understanding that the XMP files are not automatically updated beyond the information included in the Library Module unless you export your XMP sidecar files after making all of your adjustments. Hence, a critical step in a workflow with Lightroom - if you want to have access to all of the settings you've made in the Develop Module is to export the XMP sidecar files after you have made the final adjustments your images. To do this, select all of your images, then Export the XMP metadata by going to (in the menu bar) Metadata > XMP > Export XMP Metadata to Files. This will save all of your settings to the XMP file and update each XMP file.


Now, sadly, exporting the XMP sidecar files will not record the creation of Virtual Copies and the settings you made to those or any other information regarding stacking, slideshows, etc. Basically it includes all of the keywords, metadata, ranking and ratings and all changes made in the develop mode to the original RAW file. To transfer these other settings you would have to copy the Lightroom cache file along with the folder of images and load all of that onto the other machine.

An easier way of dealing with all of this is to have your Lightroom cache and the images on an external hard drive that you can switch between computers. For most of us that is impractical and if that external drive is FireWire or USB 2.0, the connection speed of either will drastically slow down Lightroom as it tries to read the cache and images from the external hard drive.

I wish I had better news on an easy way to work up your images on your laptop, then transfer those settings to your office computer when you get back from a shoot but it isn't always straight forward or easy. It can be done though. I am sure Adobe is working on this issue as we speak and hopefully we'll see an easy solution to this issue in an update or Version 2.0.

For my work, I can generally wait to get back into the office and download my images to my imaging machine and keep all of my Lightroom settings on that computer. If a client needs images while I am in the field and I have to work them up on my laptop then I will do so but otherwise everything runs through my imaging computer in the office. For most clients I explain that for the best image quality and color management it would be best if I don't work the images up on my laptop and I wait to do that work back in the office. Hopefully laptop displays will get better and that will change but so far I haven't seen a laptop screen that can compare to my Apple Cinema Display in terms of color accuracy.

That's it for this week. I hope this helps to clear up a few issues with the XMP sidecar files.

Adios, Michael Clark


Andrés Vattuone
2007-05-07 02:41:30
I am glad that you have driven our attention (and hopefully Adobe´s) to this topic. I believe xmp sidecars are a key feature. It would be nice to add virtual copies, snapshots and history info to xmp files and beeing able to transfer info to other libraries. Splitting and merging of libraries would also be great.
Jo Wu
2007-05-07 16:32:55
Would saving s Lightroom library under/as a CS3 Version Cue "Lightroom" project a viable way to synch all info between desktop/laptop?
Carol Parker
2007-05-07 22:44:48
Thank you, Michael - you certainly answered my question of last week re XMPs in depth! I sure hope Adobe addresses this issue in the near future! Just want to say that the Inside Lightroom website with the thorough and thoughtful blogs is just terrific - at the top of my list of Lightroom resources. Thanks!
Carol Parker
Kim Guerrette
2007-05-08 17:52:13

If you did have to work up an image on your laptop, how would you get that image's data onto your imaging-computer if you happen to have also made virtual copies? Sorry, I haven't taken the time to mess with the cache, but I guess I was concerned with the existing cache on your imaging-computer. Can you merge caches? I'm guessing not.

One way to get around this (and not the only) would be to copy the cache from your imaging-computer to your laptop, do your shoot, edit your photos, then when you get back copy your updated laptop cache on top of the now stale cache on your imaging-computer. Then move your photos into your file structure on one of your imaging-computer's HDDs and relocate the "missing" files in Ligthroom on your imaging-computer. Would this work?

Thanks for the info.

Michael Clark
2007-05-09 14:25:01
Kim -

To do this I would copy the Lightroom cache as well as the images and their XMP files to my desktop then select in the Lightroom Preferences (under General) that Lightroom ask me when it startes up which Library I'd like to choose - then I'd select the one from my laptop and point Lightroom to the images I had transfered as well - that should do the trick I think.

As far as I know you cannot merge caches. Your second paragraph (method) would work just fine I think. The only probelm is carrying around a hard drive with a few terrabytes of info on it would be a little dicey for the info on that hard drive. If all of your digital images fit on a smaller hard drive then that would be great - just make sure you have them all backed up on another drive since lots of travel and hard rives don't mix too well.

Micheal Clark
2007-05-09 14:26:36
Jo -

Sorry, I don't have any experience with Version Cue. If that does work please let us know - that would be pretty sweet.

John G. Walter
2007-05-10 13:28:07
Copying databases back and forth has got to be a management nightmare. Until Adobe figures out some way to make it work, I would stick to the limitations of Lightroom's 'virtual' enviornment.

Wouldn't some kind of 'Export' of a Collection be a possible answer?

On another note, from my comment in your earlier SideCar post, I don't really see what is happening when I choose Metadata > XMP > Export to a file.

Changes seem to be applied to the XMP files immediately. What editing functions require this additional step?

Michael Clark
2007-05-12 21:02:15
I thought all editing changes were applied to files automatically as well with the XMP sidecar files but on my last try to re-import some images it seemed that they didn't have all of the changes I had made to them and I realized that the Library changes were recorded but Develop mode changes were not - hence the need to export the XMP sidecar files at the end of the workflow.
John G. Walter
2007-05-14 09:58:55
I guess not. As an example, I cropped a PSD file. Unlike PS, there does not seem to be an 'accepting of the crop', as the crop marks just remain there on the image in the Develop module. The thumbnail or the larger preview in the Library module, shows the image cropped.

However, this action does not seem to write to the XMP file, nor does it get updated by an XMP export. This would leave me to believe that it is only contained in the LR database, however, when I moved the files to another computer, the crop data moved with them. Very confusing???

Then, I moved the files on the target computer from one folder to another, and now the crop data disappeared.

Could the problem be with me missing an XMP Export at some point, or in how I handled the file movement on the target machine?

Michael Clark
2007-05-14 10:04:35
John -

My answer is I don't know. Hard to say not having watched exactly what you did. I'm sure Adobe is working on this whole issue so hopefully it will become a non-issue here shortly.