Reduce your Camera Roll backup
To check the amount of storage iCloud uses to back up your iOS device Camera Roll, go to Settings > iCloud > Storage & Backup, then tap Manage Storage. Tap the name of your iOS device, then look below Camera Roll in the Backup Options list.
To reduce the size of your Camera Roll backup, you can delete photos or videos from the Camera Roll on your iOS device. You can also import photos from your Camera Roll to your computer, and then delete them from your Camera Roll. For instructions, see the Apple Support article iOS: Importing personal photos and videos from iOS devices to your computer.