Dual capture is automatically on. This means that Lumia Camera stores both the 5MP photos and the full-resolution photos. If you don’t want to save the full-resolution photos, you can switch dual capture off. In Lumia Camera, tap … and settings. To switch dual capture on or off, change the setting for Capture mode.
Note: This applies to Lumia Camera in the Lumia 1020, Lumia 1520, Lumia 930 and Lumia Icon.