When you first time launch Photos app, it will ask you to choose which library would like to import into Photos app. Once you choose your library, you can not import another library into Photos. That means, if you choose iPhoto Library while launching Photos app, then you can not import an Aperture library into the Photos library. But, you can create a separate Photo library and import your second library into that. To do so, hold down "Option" key when launching the program.
If you have trouble with Photos app stalling during an import, then you can rebuild your iPhoto Library. To do so, launch "iPhoto" and hold down "Option" to select a library, then hold down Command and Option when clicking "Choose" button. Choose "Rebuild Database" ooption to repair the iPhoto Library.
Steps to Export Photos from iPhoto Library:
- Open "iPhoto" on your Mac.
- Select all photos and choose "Export" option.
- Choose "Original" or "Current" option from "Kind" pop up menu.
- Click "Export" button.
- Choose a destination and click "Ok" button.
- Drag the exported photos into the "Photos" library or you can click "File" and then select "Import to select" option to import them.
- Repeat this process for each library.
Steps to Export Photos library:
- Option-launch "Photos" app on your mac.
- Select "iPhoto Library" which you want to merge with another.
- Once conversion is done, choose "View" option.
- Select "Albums" and double-click "All Photos".
- Choose "Edit" option and then select "Select All" option.
- Here you have 2 options.
a) Choose "File" menu and select "Export Unmodified Originals" option and then click "Export" button. This will exclude all changes to an image made within Photos or imported from iPhoto.
b) Choose "File" menu and select "Export [number] Photos" option. Now select a file format and click "V" the expansion triangle and then select "Full Size" option from the Size menu. It will export all photos into eight .jpeg, .png or .tiff file formats, rather than the original file format.
- Choose a destination to export your photos.
- Close "Photos" app and re-open it with the library which you want to merge into.
- Drag the exported photos into the "Photos" library or you can click "File" and select "Import to select" and import them.