Both Olympus TG-850 iHS and Sony NEX-5T have 16.0 MP resolution sensors but Olympus TG-850 iHS's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Sony NEX-5T's sensor is APS-C (23.4 x 15.6 mm ).
Since Sony NEX-5T's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Olympus TG-850 iHS.
Below you can see the TG-850 iHS and NEX-5T sensor size comparison.
As seen above, Sony NEX-5T has a 13.0x Larger sensor area than Olympus TG-850 iHS. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.