I’ve been a fan of using Lightroom Mobile for almost a year, even since Adobe allowed RAW photos to be imported into the application. The process is faster, the editing is more intuitive, and the connections with iOS share sheets make sharing photos from my DSLR easy to do, even when on the road. I’m so happy with the app I even left my MacBook at home during my recent trip to Portland, Oregon. I also left it behind when we headed to Williamsburg. I never skipped a beat.

Until, that is, I got a warning from iCloud, “You have only 383 mb left of storage in your iCloud account.” This set off some alarm bells.

The temporary solution was simple. Lightroom Mobile was set to sync with iCloud, which is not something I really need. My Lightroom Library is backed up in two time machine installs, and CrashPlan. iCloud backup was nice, but more redundant than I required ¹. So I turned it off.

Once that was fixed I went searching for the cause. Why was Lightroom Mobile taking up so much storage? It turns out, I was using it wrong ².

When I import photos into Lightroom I add them directly into a collection created to receive them. This collection is then automatically set to sync with Lightroom’s Desktop application, and makes managing the photos easier once I’m able to return and update my library. I figured once I disabled sync for the collections, the included photos would be removed from my iOS device.

What I’d forgotten is how Lightroom allows users to manage photos by both collections and folders. In Lightroom desktop, folders deal with the actual file structure of a drive, though with some metadata which speaks to the Lightroom Database and tells the application where photos are when they are moved ³. Collections, on the other hand, are a depiction of the Lightroom Database itself. They can be sorted, moved, and deleted without impacting the actual photos themselves.

It turns out Lightroom Mobile works with photos in a similar way. In the app there is only one folder, “Lightroom Photos,” but it functions the same as any folder on the desktop application. Every photo imported into the application physically resides in that folder, regardless of any collections in which individual photos may reside ⁴. I hadn’t been paying attention to the consistent language Adobe was using across platforms. Instead, I was treating mobile collections as folders. Thus, when I disabled sync on a collection, the photos remained ensconced in my Lightroom Mobile library. After almost a year of importing photos into Lightroom Mobile, my storage had finally run out.

This led me to a quandary. Was it safe to delete photos from the Lightroom Mobile library without having it impact my full library? It turns out, yes, you can. The “Lightroom Mobile libarary” is the data with which the mobile application interfaces. Whenever a photo is synced from the desktop application, or imported into the mobile application, it’s added to a different library which is synced with the user’s full library via their desktop application. This library exists in sync with, but independent of, the desktop library. It is the bridge through which photos travel between devices. In fact, these photos can be manipulated in any browser via Adobe’s excellent Lightroom web-application.

So if photos imported into LR Mobile exist in a semi-independent state from the full library, when will it be safe to delete them? When photos are imported into the desktop application they are downloaded into their own folder in the Lightroom library, “Lightroom-Mobile ⁵.” This folder resides in the root directory of the drive in which the Lightroom library reside, and photos in it can be moved, reordered, and renamed at will. And, while name and metadata changes will be synced between the the mobile and desktop libraries, physical moves between folders will have zero impact on a photo’s existence in the mobile library. When all the photos have been synced between the LR Mobile and LR Desktop libraries it’s safe to delete the photos from the Mobile library. And thus, the mobile device. A fair warning, before deleting photos from the mobile library make absolutely certain every photo has been synced. Pre-mature deletion could lead to much sorrow and gnashing of teeth. Also, if you have organized your photos into collections, be sure to halt syncing these before you delete anything from the mobile library. Deleting photos from the mobile library also removes them from any associated collections, just as on the desktop application. When syncing is photos won’t be removed from any associated collections ⁶

Having tamed the LR Mobile library, I’m even more excited to see what I can do with this wonderful tool.