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Revisiting the XMP Sidecar Option
While hanging out with my good friend Nevada Wier last week, we talked about Lightroom and some tricks she learned while teaching her last photo workshop in India with George Jardine, the Adobe Lightroom evangelist. One of the options she told me about was leaving the "Automatically write changes into XMP" box unchecked in the catalog preferences which is its default mode as in the image below.

In version 1.3, checking the "Automatically write changes into XMP" box doesn't slow the program down nearly as much as it did in earlier versions. But if one would like to get the most out of Lightroom in terms of speed then there is another option which is basically to leave the box unchecked, and every once in a while go to "Metadata > Save Metadata to File" if you still want the XMP files saved out to the folder where your original images live.
This novel idea achieves the same results as using the XMP automatically but allows Lightroom to run at the maximum speed. The only downside is if Lightroom crashes or freezes for some reason and you haven't saved the XMPs then you have lost all of your work for that session. Other than that which is rare, this is a slick way of making Lightroom run just a bit faster. And once you "Save Metadata to File", then the XMP files are built next to the raw images just as they were with the "Automatically write changes into XMP" box checked - hence, when browsing the images with Bridge CS3 the worked up raw files appear as they were processed in Lightroom.
As this is a critical part of my workflow, up until now I have had the xmp box checked all the time. In my next session using Lightroom I plan to give this new idea a spin and see if I notice a performance bump. If so then I might very well alter my workflow and write my self a post-it note so I remember to "Save Metadata to File" often.
That's it for this session. See you next week.
Adios, Michael Clark

Thanks for the blog entry. I found with previous LR editions that there was indeed a huge hit on speed with the box checked. But with 1.3.1 and 10,000 images in the database, I have noticed no slowdown with the automatic feature checked. How delightful this has been, because now I don't have to remember to save to the metadata file. I used to regularly forget
I do use a very fast machine however and only use DNG files. Cheers
Michael,
Users that have this option already switched off will see a huge hit in performance if they switch it on with a largish catalog. If someone wants to use this option, they should do it when they will be away from the computer for a while. Then turn it on and let it go, because Lightroom will beginning to export XMP to all files. You could, of course, simply go to All Photographs and Cmd/Ctrl A to select all and then Cmd/Ctrl S to save out all the info. When it's done switch on the Auto option.
Does Lightroom really lose your changes if it crashes? I thought it saved to its own database, and XMP was only useful for external programs.
Peter -
Good question. I have not seen this with Version 1.3 but a friend had Lightroom crash (V1.2) and she only recovered the work she had done because she had the XMP metadata box checked - she had to reimport her images into a new catalog so I am guessing the answer is yes. If anyone else has a different experience please let us know.
Cheers, Michael
Hmmm, she should have plenty of earlier versions of her catalog in the "backup" folder. That would have saved her everything up to a day or week ago... Or did she explicitly deactivate that fallback?