For a good six months I have been attempting to follow a tortuous thread at the Leica Forum on the subject of using Leica lenses on the Sony A7r full-frame camera. By rights, the Sony should be a natural: Leica M lenses at their designated focal lengths, just as nature and Oskar Barnack intended. None of this crop-factor nonsense where 35mm primes become nifty fifties or, even 70mm short teles if you are using a Micro Four Thirds camera. No, with the Sony A7, full-frame lenses are in their heaven and all is well with the world. Almost.

I confess to starting one of the several threads that were eventually merged into this unstoppable juggernaut that has now exceeded a wordy 225 pages. At a rough estimate it would take two months to read through all the ramblings of contributors who have been pixel-peeping and nit-picking for all their worth over these months in this D-Day assault on the beaches. There is nary a sign of an ebb tide. I suspect some of them have never touched a Sony A7r and quite a few have probably never owned a Leica M lens. On the other hand, credit where due, many do know what they are talking about and hold views that I respect. In no way would I want to belittle their contributions.
Today, forum member biglouis, also known as LouisB, asked a very simple and reasonable question, one that could have been asked sooner?
I’ve tried searching this thread to get an overall opinion but I can’t find examples (easily in 225 pages). My question is the prevailing evidence about whether or not either the Summicron 35 or Summarit 35 work well on the A7. I have a FE 35/2.8 but I am not happy with its character. I also have a C-40 Summicron which works well (very sharp, no smearing or colour shift). However, even though it is only a 5mm difference I do find it a tad restricting. Can anyone post samples of the A7 with either of the two Leica lenses – or point me at examples?
Yes, indeed, why not. Truth be known, I haven’t had much difficulty in using Leica M lenses on the Sony A7r. It is a a great little camera (it is indeed little when compared with a Leica M) and has outstanding image quality. Leica M lenses only add to this calibre. It is possible to nitpick but, in general, I have enjoyed outstanding results. In the main I have used my 50mm and 75mm Summicrons and it is well accepted that these longer lenses play better with the Sony than wider optics. Of course, the Sony is not made specifically for Leica lenses and there is no attempt to correct inherent deficiencies. Any successes are pure happenstance. But, frankly, does it matter most of the time? I do wonder.
So, back to pussycats. Look at Mr (or is it Miss) Pussy in this photograph (I was so busy focusing that I didn’t check the flavour, although cat sexing is an arcane pastime at the best of times). What is wrong with this shot, taken at Easter in Greece? Would it have been better had it been taken with a Sony Zeiss lens? Or with a Leica M camera? Or does the true signature of the Leica 50mm Summicron-M ASPH come shining through whatever camera it is bolted on? If I may poke my head above the trenches for a moment, I do think that the touch of the Summicron there.
I am sure someone will tell me about chromatic aberration, distortion of whiskers or other serious defects that will have me drummed out of the Barnack School of Photography. But I like this portrait of a pussy and perhaps that’s all that matters. When the chips are down the Sony A7r does indeed play well with Leica lenses.
That shot looks great to my eyes. I must say that I really struggled manually focusing the 35 Summaron on the Nex 6, even with Sony’s supposedly excellent focus peaking.