Originally posted by UncleVanya What appears to be the case is that this is mostly a non issue when using adapted SLR or DSLR lenses on Sony. It is more of an issue with Leica M lenses on m4/3. Basically if the sensor glass thickness is significantly different, there can be an optical effect.
Sensor Stack Thickness: When Does It Matter?
Oh and the closer the exit pupil to the sensor, the more impact this has. Slr wide angles with their retrofocal designs are typically less impacted than rangefinder wide angles.
Depending on how picky one is with edge sharpness, it can/does affect even SLR lenses (at least the Pentax K mount ones).
I have compared the results shot on my K24/2.8 on a modded and non-modded A7, and there was a slight difference.
In comparison, this same K24/2.8 does perform better on the K1 than the modded A7 when the file is reduced to 24mp.
I've also seen samples passed to be from the A7r with the K24/2.8 (also a 36mp sensor) and they were outright horrible on the edges (unlike the K1)
The effect for old RF wides are significantly worse, thats for sure.
That said, the newer RF lenses designed to cater for this (and out for many years already ) does take care of the issue.
Some examples being the latest versions of the Voigtlander 10mm,15mm, 21mm.