Leica S2 has a 38.0MP Medium format (45 x 30 mm ) sized CCD sensor . You can shoot at maximum resolution of 7500 x 5000 pixels. S2 has a native ISO range of 80 - 1250 and it can save files in RAW format which gives you a wider room for post processing.
Leica S2 is not the highest resolution Medium format camera. Fujifilm GFX Eterna 55 with its 102.0MP sensor is leading in this class. Check the comparison of Leica S2 vs Fujifilm GFX Eterna 55 or take a look at Highest resolution DSLR cameras list.
Leica S2 DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Leica S2 sensor has been tested by DxO Mark and got an overall score of 76 for its image quality. You can find the details of their analysis of Leica S2 here.
Let's look at how the size of the Leica S2's Medium format sensor compares with other standard sensor sizes.
Comparison image of Leica S2 Sensor Size with other standard sensors
Sensor size is what determines the circle of confusion, and therefore how much
depth of field Leica S2 gives you at any given aperture.
You can
calculate
the exact depth of field for the Leica S2
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.
