iCloud Photo Library Sharing


Hello All,
I have 27" iMac 17,1 spec as follows,
i7 4GHz
AMD Radeon R9 M395X 4096MB

ok so I'm very confused as to how iCloud Photo Library works and what happens when it's enable and I delete photos locally on my Mac.

I have a big problem as lately my machine has almost run out of HD space, iPhoto Library on my iMac is almost 500GB!!
I have over 92,000 Photos. I admit I do need to go through them and delete stupid things like screenshots and photos that I have copies of from shooting with my iPhone where it takes 4-5 shots of the same photo but that's for another day.

What I really want to know is How it all works, if I take a photo form my iPhone and have iCloud Photo Library enabled what exactly happens in easy terms!

I just find the whole thing confusing I'm dealing with iPhoto, iCloud, iCloud Photo Library and I'm scared that if I delete anything from either iCloud or iphoto I'll lose my photos. I take a lot of family photos of my kids and I treasure them.

I have iCloud Photo Library enabled on my iMac and iPhone and I also subscribe to Apple's iCloud Storage 2TB, I also have Family Sharing on.
My Wife and 3 kids also have iPhones and iCloud Photo Library enabled and are all linked in to the Family Sharing too.

For now I'll start with just me and I can explain then to the rest of the family once I know more.

If I take a Photo from my iPhone it stores the photo locally on the phone and also pushes to the iCloud and as I have iCloud Photo Library enabled on my iMac it downloads to iPhoto library on my iMac. This much I get.

Now say over time I build up we just say 2,000 photos. These are on my iPhone, iCloud and on my iMac and all synced and all backed up via Time Machine and a Drag and Drop copy of iPhoto Library to an external drive. Happy Days!

What happens if I delete a photo from my iPhone? Is it the case that when my iCloud syncs the photo is also deleted from my iCloud and then eventually deleted from my iMac? if so is it the same if I delete a photo from my iMac in iPhoto? when it syncs is it also gone from iCloud and iPhone?

I recently physically copied my 500GB iPhoto File to an External Drive and then went in and manually deleted all the Master Files from the Show Package Contents of iPhoto Library on my iMac, but when I go into iPhoto all my Photos are still there but my HD Space is 500GB less? how is this possible?

I do apologise for the large post.

iCloud is a syncing service. It is not a storage place. So if you delete from your phone, it will be deleted from iCloud and your Mac.

What you can do is get an external drive just for storage of your photos. You can use the Photo app to archive specific photos (say from two years and older as an example) and save it to the external drive.

When you delete the 'Master' you need to clear the deleted folder in Photo app similar to emptying the trash. Even when you delete an old download from your Mac, it is still there until you empty the trash.