Samsung Galaxy S6 uses a Sony IMX240 camera sensor

Barring the Galaxy S5 which used Samsung's own sensor, the Galaxy S6 has reverted back to using Sony's camera sensor. The Galaxy S6 and Galaxy S6 Edge use Sony IMX240 camera sensor also seen on the Samsung Galaxy Note 4.

Samsung Galaxy S6 Specs and Photos

Although Samsung has worked on the camera module and has given it a wider aperture up from f/2.2 to f/1 which would help with low-light photography. The front camera uses a Samsung made 5 MP SLS_S5K4E6 sensor which seems to be the same found on the Galaxy A series of smartphones.