I just recovered iPhoto on 2 computers (1 laptop and 1 iMac) by basically following steps previously mentioned by others. Both computers are running the latest OSX, 10.11
Basically, just do the following:
Go to App Store > Purchases > iPhoto App > Install or Upgrade
After it installs, go to your application folder and open iPhoto. You will be asked to choose or create a photo library. Just choose the original one and it will take care of the rest.
Having talked to a friend who is a graphic designer. And myself an Art Director I highly suggest you put all your photos on external drives as a backup.
Mac is pushing and pushing the cloud is very annoying. I had to reimport my photo's again onto my 27" iMac don't know why.
I use an older iPad of reference. Don't want it to participate in any of this Apple cloud stuff with this machine it is shut off. Over and over a window asked me to sign on to the Cloud. I gave up and shut off the machine.
Your original photos are never were in iPhoto or Photo. This is just a catalogue. They are in users/pictures in your hard drive.
Put that on an external.
The other issue if pictures and music which Apple has been trying to control. By forcing you to use the cloud you have a glut of memory which they wan't you to pay more for on the cloud.
Running latest Mac OS capitan on Mac 27 with 16 Ram.
When I try open it tells me my iPhoto has been migrated to Photo. True but this is interesting. I sometimes load clips and photo's into iPhoto for a quick preview. I tried to take photo's off of Photo I needed a few for a spot. It couldn't be dragged off.
Googled it what you do is select a group and export this take a while looks like nothing is happening. But on top bar their is a progress button that opens?? It shows you are transferring to desktop or I think may need a folder. I highly suggest everyone go to used and find their photo master file. Mine had 50 gigs.
And put on a good external drive. Mac has dumbed photo down so they can sell consumer services more intrusion in what used to be a very workable computer.
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