DEFINITIVE SHOOTOUT: Leica SL2 vs Panasonic S1R Sharpness with Leica SL Lenses: View North Over Puppy Dome
The issue: ray angle interacts with the sensor cover glass thickness; a lens is designed assuming a specific thickness. Deviations from that thickness degrades optical performance, particularly off-center. A secondary issue is the color rendition, which can depend both on the sensor itself, its IR-blocking layer, and the electronic processing of the camera.
One would hope that the L-Mount alliance would have standardized on sensor cover glass thickness and characteristics, so that lenses of either brand could be used with the same results on either-brand camera. But in marketing, form trumps function.
Definitive finding: Leica SL lenses
Includes images up to full camera resolution from f/2 through f/11, plus crops.