If you wish to delete photos from iCloud, but not from your iPhone or iPad. So you can free iCloud space, but have them actually saved on the device then they are perfect in my opinion. To do it, you’ll need to disable the photo syncing option. Follow these steps is how to delete photos from iCloud but not the device -

1. Tap on the gear-like icon on the home screen of the iPhone or iPad to open the Settings app.

2. Swipe down and select the Photos tab from the list.

3. Slide the iCloud Photos button to the Off position.

4. If you want to remove the low-resolution copies of the photos from your iPhone all together, you should tap the option that says Remove from iPhone when the pop-up message appears. The originals will be kept in iCloud.

5. In the options that appear choose the Download Photos & Videos back to the device option to retrieve the original picture.