Samsung Galaxy S6 uses a Sony IMX240 camera sensor

The Galaxy S5 launched with Samsung's own camera sensor, however it seems that its successors have reverted back to Sony. The Samsung Galaxy S6 and Galaxy S6 edge pack a Sony IMX240 sensor, the 16MP unit we've seen on the Galaxy Note 4.

Samsung has improved the camera module since the phablet though, widening the aperture from f/2.2 to f/1.9. This should further help low-light photography, which already enjoys the benefits of optical image stabilization.

Galaxy S6 reporting a Sony IMX240 sensor

In the previous generation the Galaxy S4 used a 13MP Sony IMX135 sensor.

The selfie camera on the Galaxy S6 reports a SLS_S5K4E6, which indicates a Samsung sensor. It's a different sensor though, a 5MP one instead of the 3.7MP sensor in the Galaxy Note 4. It's most likely the same selfie camera that goes into the Galaxy A series.

Source