Ray angle of rangefinder lenses interacting with the relatively thick sensor cover glass of the Sony mirrorless cameras introduces severe astigmatism in outer zones, along with lateral chromatic aberration.
Astigmatism can be understood as “two planes of focus generating a double image”. These are the sagittal and tangential foci, as used in MTF charts.
A specially modified Sony A7R II (KolariVision) and a stock unmodified A7R II were used to explore the performance of the Leica 50mm f/2 APO-Summicron-M ASPH. This is not a lens review, and is targeted strictly at showing how the modified camera performs.
This detailed analysis should answer the questions I’ve been receiving from those looking to shoot Leica M lenses on Sony mirrorless.
The Leica 50mm f/2 APO-Summicron-M ASPH was used for several reasons:
- Many Sony shooters using M lenses deceive themselves: there is a myth making the rounds that somehow a 50mm rangefinder lens is not affected by ray angle; that this is false is demonstrated beyond a doubt.
- The Leica 50/2 APO is Leica’s highest performing lens.
- Wider-angle rangefinder lenses (35mm, 28mm, 24mm, 21mm 18mm) will be affected more than a 50mm, hence if a 50mm looks bad and it being a more favorable case, wider angle lenses will see even more benefit.