I posted this earlier on another thread but ut may help here too. The comments refer to various adapters used on my Nex7 but they will no doubt apply to the a7(R) too.
I have two adapters for Leica-M to E-mount, a Metabones and a Voigtlander, and I use a Novoflex adapter for Leica-R to E-Mount. The following comments are, of course, specific to my adapters, and there may be variations in other copies.
I tested a Minolta M-Rokkor 40/2 for an infinity shot throughout its aperture range on my NEX-7, tripod mounted with both adapters. First observation is that the Metabones adapter gave perfect focus at infinity whereas the Voigtlander adapter allowed focus beyond infinity. Secondly the Voigtlander adapter is apparently de-centred - the focus on the right edge of the frame at wider apertures is always softer than on the left. Generally, the lens behaved extremely well and showed excellent centre sharpness wide open on both adapters with good edges but soft corners with the Metabones and slightly less good edges and corners with the Voigtlander adapter. This comparative behaviour continued as the aperture stopped down so that at f5.6, when side sharpness became excellent with the Metabones it was merely reasonably good with the Voigtlander. The optimal aperture for sharpness is f8-11. The best corner sharpness was achieved at f8 with the Metabones producing a very good showing while the Voigtlander corners could only be described as good although both became very good at F11. The Metabones is clearly better than the Voigtlander performing better at all apertures up to F11 and also suffering no de-centring problems. The only benefit of the Voigtlander is that infinity focus is always guaranteed since it can go a little beyond. There is no such flexibility in my copy of the Metabones. This presents no problem with the Rokkor-M but might do with other M-mount lenses. This is, however, not really an issue for me as I rarely do infinity shots on the Nex.
For comparison, the Leica R 50mm F2 Summicron performed impeccably at all apertures with the Novoflex adapter on the NEX and seemed to be at optimal performance by F4, where it matched the Rokkor at F8. Like the Voigtlander, the Novoflex allowed focus beyond infinity.
Herb1911 wrote:
I use Novoflex adapters and one Voigtlander that is also well made.
Will check infinity hard stop for all lenses. In progress. Sofar I am sure of the 90mm Apo Summicron that hits the hard stop at infinity on the A7r.
