For rangefinder wide angle lenses on the Sony A7, Kolari in the US offers a special thin filter pack replacement, to make the camera more compatible with rangefinder wide angles. See this link:
http://kolarivision.com/product/sony-a7-series-thin-filter-legacy-lens-upgrade/Nikon S mount as well as Voigtländer and Leica L39 and M mount wide angles will benefit from this modification, which is done much the same way as UV/IR mods of cameras.
Native E mount wide angles are retrofocal lenses with a short back focal distance and thus will not produce smearing or astigmatism in the image corners with Sony's stock sensor filter. Leica M wide angles and old Rangefinder wides are not computed with a thick sensor cover in mind and will in combination with the stock sensor cover produce unwanted astigmatism and smearing. Astigmatism and smearing can't be digitally corrected.
The new Zeiss Batis Distagon 25/2 and Zeiss Loxia Distagon 21/2.8 are examples of weakly retrofocal lenses with short back focal distance that are computed with Sony's thick sensor filter in mind, and these produce excellent imagery into the extreme full frame corners. Traditional Leica M wides are not and need a sensor cover mod.
