Both Pentax MX-1 and Fujifilm X30 have 12.0 MP resolution sensors but Pentax MX-1's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Fujifilm X30's sensor is 2/3-inch (8.8 x 6.6 mm ).
Since Fujifilm X30'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 Pentax MX-1.
Below you can see the MX-1 and X30 sensor size comparison.
As seen above, Fujifilm X30 has a 1.4x Larger sensor area than Pentax MX-1. 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.