How to stop my iPad and iPhone from automatically syncing photos?

I have just purchased a new Mac and I am gradually transferring photos from my old Windows pc, before disposal, to the Mac and organising at the same time. On the Mac I currently have iCloud sharing turned off, but I’ve noticed that as soon as I import photos on to the Mac they are automatically copied to my iPad and iPhone. I am concerned about storage on my other devices. How can I stop this automatic syncing occurring?

[Re-Titled By Moderator]