Apple’s abrupt discontinuation of the photo editing and library management tool Aperture—software designed to hold hundreds of thousands of photos—left many professional users without many options, other than to convert their photo libraries to competing apps. As the chief beneficiary of Aperture’s impending demise, Adobe has released a migration guide from Aperture to Adobe Photoshop Lightroom, walking through a manual export of photos from Aperture, then importation into Lightroom.
An automated migration tool is currently being worked on, as well, so you can skip the guide if you’d rather wait for Adobe to release the app.
If the idea of switching from Aperture to Lightroom wasn’t jarring enough, just wait until you read the part of the Adobe guide that explains how already-applied Aperture photo adjustments can’t be read by Lightroom; the workaround is to “export adjusted versions as high-quality 16 bit .tiff files,” then organize the original and adjusted photos to appear next to each other.
Expect your exported photo library to swell in size as a result. You’ll also have to manually apply some keywords to images, because Lightroom can’t read Aperture’s color labels, flags, or custom metadata fields.