Pentax K-S1 has a 20.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Prime MII processor. You can shoot at maximum resolution of 5472 x 3648 pixels with aspect ratios of and 3:2. K-S1 has a native ISO range of 100 - 51200 and it can save files in RAW format which gives you a wider room for post processing.
Pentax K-S1 is not the highest resolution APS-C camera. Fujifilm X-E5 with its 40.0MP sensor is leading in this class. Check the comparison of Pentax K-S1 vs Fujifilm X-E5 or take a look at Highest resolution DSLR cameras list.
Pentax K-S1 DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Pentax K-S1 sensor has been tested by DxO Mark and got an overall score of 78 for its image quality. You can find the details of their analysis of Pentax K-S1 here.
Anti-Aliasing Filter
Another important feature about Pentax K-S1's sensor is the lack of anti-alias (Low-pass) filter. Removing anti-aliasing filter increases the sharpness and level of detail but on the other side it also increases the chance of moiré occurring in certain scenes.
Let's look at how the size of the Pentax K-S1's APS-C sensor compares with other standard sensor sizes.
Comparison image of Pentax K-S1 Sensor Size with other standard sensors
Sensor size is what determines the circle of confusion, and therefore how much
depth of field Pentax K-S1 gives you at any given aperture.
You can
calculate
the exact depth of field for the Pentax K-S1
at any focal length, aperture and subject distance, including the hyperfocal distance
for landscapes and the very shallow focus zone you get with long telephoto lenses.
