I've been using Aperture ever since I got my iMac, which was about two years ago. At that time, I moved all of my digital images from a "folders and files" disk hierarchy into my Aperture library, and continued to add and catalog every image since. My library contains a little under 42,000 images in an image library that takes up almost 300GB -- most of which are probably garbage.
When Lightroom 4 came to the Adobe Cloud, I decided it would be a "good thing" to make the move. This was not an easy choice, as I've invested in several sets of "presets" for Aperture, as well as having done alot of image editing in Aperture. And, while the results of those edits will be retained, there will no longer be "back links" to the original files.
Obviously, there must be compelling reasons to switch, right. Why, yes, of course there are. Lightroom is cross-platform, and through the Cloud, it will eventually be quite easy to move images collected in the field on my Acer laptop to the iMac (and back, if needed), including any post processing. There are a number of plug-ins and add-on items for Lightroom. And going back-and-forth between Lightroom and Photoshop is a snap.
So, what's the big deal? Open Lightroom and import the pictures, right?
Not so fast, buddy! Seems that when I set Aperture up, I elected to store my images "in the Aperture Library," which means that all 42,000-ish images are stored in a special kind of Mac directory called a "package." While that's an easy format to deal with for some Apple software, Adobe programs can't look inside a package to see the individual contents.
After a fairly exhaustive search of the Aperture "documentation," and several sources on the web, I came to the conclusion that the process of moving the images was going to be a long one, and it was going to be just that: a process with several steps, none of which would be particularly quick.
The first step is to make the "Master" images become individual files on my hard disk and have them be "Referenced Masters" in Aperture. Fortunately, this is pretty easy to do using the "Relocate Originals" command in the file menu. And, it only took twelve hours. Yeah, twelve. But, the result was that all my original images were back to the old folders-and-files on the disk format and out of the previously huge Aperture library file. The Aperture library still contained my "Versions" (information about my edited images and any files that were created from the Masters using external editors), references to the original files, thumbnails and various other metadata.
Of course, I wanted those finished images to be available to Lightroom as well, so I had to export those. I chose to make them export as Photoshop PSD files, stored alongside the Masters. Obviously the records of all the individual adjustments would be lost (or, rather, invisible to Lightroom and Photoshop), but I'd have uncompressed, full-resolution versions of the images for later use. If there's a need, I can always go back into Aperture to see what I did -- all the images still appear in Aperture as they always did, but now they're references to the disk files. That took nine hours.
The final step to getting the images out of Aperture was to marry the various metadata in Aperture to the files so it would be preserved in Lightroom. There are two ways to do this -- write the metadata into the files or write it out as XMP "sidecar" files. I elected to write the metadata into the image files using the "Write IPTC to Master" option on the Metadata menu, as I've never had really good luck using sidecars -- they get out of sync or lost or just not read, and that becomes a pain. That process ate up another nine hours or so.
At this point, I have all my image files ready to import into Lightroom. Only thirty hours of processing and about four hours of research were required. Tonight, I'll start bringing all of the images into Lightroom. Again, I'll have the option to incorporate the images into a database, or leave them as folders-and-files. You get exactly one guess about which path I'll choose this time...