I recently turned off iCloud in order to change Apple ID. I turned it back on before the photos were deleted from my Mac #1. Now it wants to reupload, but has to compare the photos to what is in the cloud. I have a huge photos library of about 700GB. I want to turn off iCloud for photos on Mac #1, let the photos be deleted from the mac, and then cull photos from the photos library on another mac which has iCloud turned on, before turning the cloud back on for the original mac. My hope is to decrease the ultimate size of the library and I don't want to wait for it finish comparing the photos it thinks it needs to re-upload. Is there any reason this won't work, or is a bad idea? Thank you for any input.