A while back Microsoft announced that the storage in the free version of OneDrive will be decreased from 15 GB to only 5 GB. The bonus storage of 15 GB extra when activating Camera Roll Backup in OneDrive will also be removed.
This was not well received by users, and Microsoft is now offering users to to keep the old storage size and the camera bonus when the new limitations are rolled out.
All you have to do is go to this link:
After you have logged in and authorized the application called preview.onedrive.com, you should see this message:
This offer must be redeemed before January 31 2016.
Note that this tip is about the consumer version called OneDrive, not the enterprise version, called OneDrive for Business.