Q: Turn off iCloud for photos

Well of course if you do not have then saved on your computer then when you delete them from iCloud they will be gone - what else could possibly happen?

Before you turn off iCloud you must download all photos as you have been told

Get help with your iCloud Photo Library - Apple Support

LN

This post by léonie explains how you can remove the iCloud Photo Library and just use Photos on your Mac.  Be sure to follow the text in bold red. 

léonie

Dec 1, 2015 9:54 AM

Re: iCloud causing havoc. How do I completely delete all photos on iCloud and start over?

in response to ezrasuncle

 

The only option to delete immediately would be to delete all photos from your library in Photos and to empty the Recently Deleted album. This will delete the photos immediately from iCloud as well. After deleting the photos from your Mac and in iCloud, sign out of iCloud Photo Library.

 

Obviously, you would have to create a copy of your Photos Library before you delete the photos from your library, so you will keep the photos on your Mac.

Switch Photos to the copied library, after you deleted the photos from iCloud.