How to import multiple libraries into Photos for OS X

[iMore.com]

iPhoto and Aperture both support multiple libraries. So what do you do if you want to consolidate them all before migrating to Photos on your Mac?

Photos for OS X does let you work with multiple libraries, but it doesn't let you import them and combine them all together into a single, unified library. At least not yet. If you have Aperture, however, you can import and consolidate multiple Aperture and iPhoto libraries there first, then get the merged library into Photos for OS X. It's a work around, but it works.

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