by Julieanne Kost
The other day a customer asked me how to decrease the size of Lightroom’s Preview file (yourcatalogname Previews.lrdata). Although I had previously posted this Quick Tip video (How to prevent Lightroom’s Previews File from Taking Over the Hard Drive), he noticed that when deleting files from the catalog, the preview file size wasn’t immediately reduced. Well, it turns out that there is a slight time delay because, if you simply remove an image from the Lightroom catalog, you can still tap Command + Z (Mac) | Control + Z (Win) to undo the removal and have the photo(s) appear back in the catalog. Therefore Lightroom waits to delay that sort of clean-up task until there is an idle moment (when you aren’t making changes), and then runs in the background, so that priority tasks have all the processing power they need.