Modified Sony A7R Sensor Glass: Impact on Rangefinder Lens Performance
Related: digital sensor, Leica, Leica M, ray angle, sensor cover glass, Sony, Sony A7R, Sony A7R II, Sony A7R III, Sony mirrorless
See the prior post: Sony A7R: Sensor Glass Thickness, Ray Angle and Image Degradation: Kolarivision Modification.
Today I shot the modified Sony A7R (“SonyA7R.mod”) against a stock Sony A7R, using six rangefinder lenses (these links are general info on these lenses, shooting results pending):
- Leica 18mm f/3.8 Super-Elmar-M ASPH
- Leica 21mm f/3.4 Super-Elmar-M ASPH
- Zeiss ZM 21mm f/4.5 C-Biogon (this lens is a worst case for ray angle).
- Leica 24mm f/3.8 Elmar-M ASPH
- Leica 28mm f/2.8 Elmarit-M ASPH
- Leica 50mm f/2 APO-Summicron-M ASPH
Every one of these lenses is affected by ray angle (including the 50/2 APO). The effects include substantial loss of resolution in outer zones (mostly due to severe astigmatism caused by the sensor cover glass), but also strong magenta color shading (vignetting by color).
In each case, the A7R.mod improved matters substantially. That’s the good news. The less good news is that color shading remains more or less the same.
NOTE: as per the “which guide” policy for the past 2-3 years, lens coverage goes into the native guide, regardless of the shooting platform. These are all rangefinder lenses for the Leica M platform and (US$20K of lenses at that), thus performance analysis goes into Guide to Leica. The Leica M context also offers commentary in context of the available reference material on each lens when shot on the native camera (Leica M), something lost when split across guides and one of the several compelling reasons for “lenses in their respective native guides”.
