PhotonCamera uses advanced algorithms for capturing and processing raw images which give unmatched HDR outputs. PhotonCamera is currently in beta stage and is having rapid development.
Features:
HDRX - This functionality enables advanced stacking of many underexposed images and creates beautiful outputs.
Utilize each camera lens, by the main, wide, macro, telephoto or even IR, a functionality not available in other open source apps.
Manual Control - Easy to use knobs to control Focus, Shutter Speed and ISO on the go.
They have released one bugfixed version per year on Github. But, as the desription suggests, the app is still in beta and thus, still has lots of room for improvement.