iCloud Photo Library stores all your photos and videos in the original and high-resolution versions automatically. It also manages the size of your library on your device by turning ON "Optimize iPhone Storage" feature on your iPhone. To download full resolution photos and videos from iCloud to iPhone, you need to select a storage setting. When you turn ON "Download Originals to iPhone" settings, it will keep your original and full resolution photos and videos in iCloud and on your device.
Here's how you can download photos from iCloud to iPhone
- Tap "Settings" on your iPhone.
- Tap "iCloud".
- Select "Photos" option.
- Click "Download and Keep Originals".
- You have another option i.e. tap "Settings" and select "Photos & Camera" and then select a storage setting.