I continue to be amazed at the results I am achieving with Capture One compared to Apple's no-longer-supported Aperture. I started out paralleling images between the 2 and, like Apple, have now abandoned Aperture completely. Everything new is processed solely by Capture One. Now comes the daunting task of migrating all of my Aperture libraries. For now, I've decided to start with just the 5 star rated images from major expeditions and bring them into a single Capture One catalog. I am doing this because the images I am getting with Capture One from the same RAW files are superior to my best results from Aperture. Here's the process:

• Open an Aperture library and filter all photos for whatever you wish. In this case, I am only chasing previously 5-star rated images.
• Select all of these photos and select "File: Export: Smart Album As New Library". Name this new, temporary Aperture library appropriately. This isolates the images you will work with from the original Aperture library which remains intact.
• Quit Aperture and start Capture One.
• Create a new Catalog or open an existing one to import the new Aperture library into.
• Select "File: Import Catalog: Aperture Library…" and locate the new Aperture library.
• Acknowledge the "Import Aperture Beta" dialog (perhaps check "Don't Show This Again").
• Wait for the import and preview creation to complete (this is pretty fast).
• Go to Recent Imports and select that import by timestamp.
• Select all of the imported images and select the (i) tool to add any appropriate keywords. I didn't use keywords in Aperture but I find it beneficial in Capture One.
• At this point, Capture One is referencing these images where they reside in the Aperture library you imported from. Return to the Library tool and under the Folders tab, you will see Catalog and a hierarchy of folders where the images reside. At this point, the All Images count will be more than the count in the Catalog.
• Select the Recent Imports again then select all of its images. Drag them into the Catalog icon under Folders.
• This will move all of those images into the Capture One catalog structure. Emphasis here is on the verb Move. This will break the Aperture library which is why I do this from a copy instead of the original.
• Once the move is complete and the All Images count matches the Catalog count, you can delete the temporary Aperture library. You can also delete the imported "User Collection" in Capture One which was the pointer to the external files that are no longer there.
• Rinse and repeat as needed.

Alternatively you can just export the original images from Aperture and do a normal import into Capture One.

Now that the images are in Capture One, you can do all kinds of fun things. The images have retained their crop, straighten, rotation, flip exposure, brightness, highlights and shadows, definition, saturation, b&w and meta data such as star rating, keywords, IPTC data. Colors will be approximate as Capture One has a superior RAW processing engine but it will attempt to apply the settings from Aperture. You can tweak the images individually or mass edit them to get a new starting point. Select all and select Auto adjust all selected variants with white balance, exposure, high dynamic range and levels selected.

I plan to retain my original Aperture libraries for now. I'll eventually do a one-for-one migration of each Aperture library into Capture One but that will require slowing down taking new photos to make time. For now, there is no rush.