Migrating from Aperture to Photos

If you have used hierarchical keywords, like Bird > Songbird > Sparrow, after the migration to Photos, you will find three keywords on your Sparrow pictures, Bird, Songbird, and Sparrow. The hierarchy will be lost.

You have to decide yourself, how you will deal with such hierarchies in Photos. You could e.g. rename the keyword Songbird in Aperture by Bird_Songbird and Sparrow by Bird_Songbird_Sparrow, but it will be a lot of work. It is not automatic in Aperture.

The iCloud Photos Library on your external drive should not matter, as long as the drive itself has a wired connection. Put the library not on a NAS or any kind of network share, and put it not into a dropbox or ans folder, that is syncing with a cloud service. The external drive should not have been used for Time Machine backups or have any backup software installed.

Your Aperture edits will be migrated to Photos as previews. So it is essential, that you have not disabled the creation of previews in Aperture or have reduced the size and quality of the previews to save storage.

Which system version is running on your Mac? If you are still on Mojave, you can check your videos by trying to import them (the original image files) into a new Photos Library. Photos 4 on Mojave is ging a warning, if the video is incompatible with future versions of Photos and will offer to convert them.

If you have imported any audio files into your Aperture Libraries, for example, as a sound track in slideshows, remove them from the library.

As to the photos formats - there may also be problems. generally, TIFFs, JPEGs, PNGs, and any supported RAW format will continue to work, but even these image files may be causing problems, if they are using colour sync profiles, that are no longer installed. This could easily happen, if the photos are scans or or have been edited with third party plug-ins or external editors. None of my PDF images could any longer be imported, also most scans that my father has sent me, image with the extension BMP or PICT.

I had to weed out quite a few photos, that were causing Photo's background processes to hang.

I would do any conversion while still running Mojave, where you still have the corresponding color sync profiles and support for legacy media formats installed. To get an idea about potentially problematic you may want to check this iMovie document: About legacy media in iMovie for macOS - Apple Support

I could not find any similar document for Photos, but as I am frequently using iMovie to edit my videos, I used it as a hint, which formats should be avoided.

To search systematically, smart albums can help:

How to Weed out Legacy Media in Photos for Mac - Apple Community

Keywords in Aperture are hierarchical:

https://scottdavenportphoto.com/blog/2014/2/28/aperture-and-hierarchical-keywords

Any PICT images? 8^)

Hello my name Donka Nikolova. wellkome to Zoom