importing iPhotos into Photos

Okay; thank you; I understand what you said. I have two questions: #1, do you recommend that I delete the import into the new mac such as it stands now (with the ominous "iPhoto Library.photoslibrary_prepare" name) and start the steps you described with a clean slate? and #2, the upgraded iPhotos on the external drive have been renamed by the new mac to "iPhoto Library.migratedphotolibrary", so forgive me but I am concerned that that library has been changed somehow in the import process and is no longer usable somehow? Do you think I should delete that as well and begin again with using the iPhoto upgrade tool on a copy of my original iPhoto library, basically start over.?

Ok; sorry for the delay. Today I successfully followed these steps (thank you for the replies above) and the iphoto library on the old mac is now on the new mac; 14,000+ photos, etc.; events, albums, years, months, etc., all seem fine.

I think I understand now why you stated, "Then we can look at merging the libraries," because in the new mac, in the Pictures folder, the filename is iPhoto Library, indicating to me that somehow it is not part of Photos, even though I can view the pictures just fine. For example, in screensaver, my photos do not appear as an option.

So, if you are willing to resume this thread, I am ready for the next step. Thank you--

Okay. I beg forgiveness but I don’t know what it means to restore the old library from the backup.

I imported the images (following something I found in apple.support when I was researching how to do it): with the external HD connected to the new mac, I went to file menu, scrolled down to import, then chose the iPhoto library on the external HD.

Something definitely went wrong bc according to info "i" in the original iPhotos library, I have 10,333 photos @ 38.8 GB. In Photos on the new mac, info in all photos shows 22,871 photos @ 49.17 GB. You mention something interesting bc yes, in the Photos pane on the left, there is a lengthy hierarchy of masters, previews, and thumbnails. And as I said, at the top of the hierarchy it lists media types, then my albums, then "iPhoto Library.photoslibrary_prepare". Under that is the masters, previews, and thumbnails.

That said, I know for a fact that the import did not complete bc there are many photos that were not imported. And as I said, many of the photos are now blurry or pixelated. Also, the folders (years) and events are not well organized as I would have hoped for. When the import seemed to stop I quit and restarted but before I resumed the import I deselected "keep folder organization."

Before I started this, the only content whatsoever on the mac (as I said it's brand new) was 1,000+ photos from my phone that I don't know how they got there other than it must have synced with iCloud, but as I said I deselected copy to iCloud during the import bc it stopped and bc I don't have iCloud extra storage. I thought at the time that that was what might have made it stop importing.

I am not sure what you mean by I should restore my old library. In the old mac, I downloaded the iPhotos library upgrade tool, copied the iPhotos library to the external HD, and used the upgrade tool on the copy. I didn't dare use it on the original iPhotos library bc I wasn't sure if it would work or what it would do.

(I have backups of the original imac and its iPhotos library on two other external HD's, Time Machine on one and SuperDuper on the other, but still...)

So the upgrade tool appeared to be successful on the copy of the iPhoto library on the external HD that am only using for the purpose of importing to the new mac, and still it got screwed up.

After the failed import, on that external HD, there is now the iPhotos library that the new mac has renamed "iPhoto Library.migratedphotolibrary" with the old iPhoto icon, and a new folder that it created and named "iPhoto Library" with the new Photos icon.

The wimp in me really just wants to delete everything from the new mac and start over. The whole reason I bought the new mac was bc the old mac literally ran out of storage space and the number one thing I wanted to do was simply transfer all my photos to the new mac. Then I found out that new Photos doesn't read old iPhoto libraries...

I appreciate your replying. As you can see, when it stopped importing or appeared to stop importing I added to screwing it up by turning off iCloud setting and changing the keep folders organization setting midway through, so that adds to my thinking that maybe I should just delete the entire new library in Photos and start from scratch, correctly this time.

One. The one that I copied into the new mac as above. After uploading, the new mac named it, "iPhotos library". It has the new Photos icon.