Microsoft SyncToy Followup

I forgot to mention Lightroom’s image previews when I discussed using Microsoft SyncToy to backup your Lightroom Catalog and photos in this post. Remember I use SyncToy to backup my photos and as a “belt and braces” to make additional copies of my catalog to a USB disk drive.

Lightroom stores its image previews in a sub-directory where your catalog is located. If you use the default name “Lightroom 2 Catalog.lrcat” then the previews are in a directory called “Lightroom 2 Catalog Previews.lrdata”.

This directory tree stores previews in a proprietary format in a complex set of sub-directories. It can get huge. I have 29,674 photos in my catalog. According to Windows my Previews directory is 9.84 GB (10,576,150,528 bytes) and contains 29,688 files in 23,920 directories.

I create 1:1 previews but only store them for a week. I have no idea how Lightroom can produce so many files. I don’t know when it culls the old previews – maybe when I do a backup using its internal tool.

I don’t want to copy even the changes to that directory tree to my backup drive. If have to restore my catalog and photos I can always recreate the previews. They’re really there for performance reasons and it looks like Adobe said “disk space be damned” when they designed this part of Lightroom.

To stop SyncToy even looking at that directory tree I have marked it “hidden” using Windows Explorer. Then in SyncToy I tell it not to examine hidden directories. If I didn’t do that my SyncToy backups would take an hour.

You only need to mark the top level previews directory Hidden. Don’t tell Windows to hide all the sub-directories. It will take ages and I think they change all the time.


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One Response to “Microsoft SyncToy Followup”

  1. GB-in-TH Says:

    The Adobe Knowledge Base ( says this about the Preview files:

    “Previews are located in various folders in the Documents and Settings/[username]/My Documents/My Pictures/Lightroom/Lightroom 2 Catalog Previews.lrdata folder. They are organized and coded for the application to read, not for users.”

    Jeff Friedl ignored that and wrote a tool to extract the Preview Images – but he admits that not many people need it.

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