How can I ‘unsync’ iCloud photos between iPhone and iPad?

To unsync iCloud Photos between your iPhone and iPad, you can follow these steps:

1. Open the "Settings" app on your device.

2. Tap on "[Your Name / Apple ID]" at the top of the Settings menu.

3. Next, tap on "iCloud."

4. Scroll down and find "Photos," then tap on it.

5. In the "Photos" settings, locate "iCloud Photos" and toggle it off.

By turning off iCloud Photos, you'll stop the synchronization between your iPhone and iPad. They will no longer share the same iCloud Photo Library.

What do you mean by "Both my iPhone and iPad have separate iClouds". Are you using different AppleIDs on both devices for iCloud?

Then you Photos Libraries on both devices should be different, unless you have set up the Shared iCloud Photos Library. If you have set up the Shared iCloud Photos Library you just have to move the photos from the Shared iCloud Photo Library into the personal Photos Library, on the device where you shared them from. And disable the "Sharing from the Camera" in the Settings > APpleID > iCloud > Photos > Shared Library. Then the new photo you take will stay in the personal library on the device where the are. If you want to see them on the other device, you can the move the photos you want to share selectively to the Shared Library to make them visible on both your devices.