Leica S3 vs Leica SL (Typ 601): read noise comparison

The Leica S3 was measured at 10 ISO settings from ISO 100 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.46 DN, or 5.9 electrons at the sensor. From ISO 800 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 39,621 electrons; unity gain is around ISO 240.

The Leica SL (Typ 601) was measured at 11 ISO settings from ISO 50 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (50) read noise is 1.85 DN, or 9.8 electrons at the sensor. A second gain (dual gain) kicks in at ISO 200, cutting input-referred read noise by about 2.1 stop. From ISO 200 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 6400 don't change analog gain (digital push). Full well at base ISO is about 83,599 electrons; unity gain is around ISO 260.