There are two particularly tempting bones that the News panel of DPReview regularly throws us:

1) A new, better mid range zoom for a camera we already have.

2) A new camera that will offer improved IQ and resolution to users of much-loved legacy lenses - and for me that often means Leica M glass.

Sony has announced just such items of late and though they would appear largely unrelated, bear with me: there's a possible link that might make you think twice.

The Sony Zeiss 16-70mm OSS F4 for Nex E-mount cameras, announced a few weeks back, immediately grabbed my attention. It is no secret that some of the Nex range cameras (I have a Nex-7) offer terrific sensor IQ but have been somewhat hobbled by the lack of really good native mount glass. In particular, many of the zooms have failed to impress and have in my experience not unleashed the potential of the sensor. So when the 16-70 Zeiss was announced, I reversed the decision I had made to eBay the Nex-7 and sat back to await the arrival of the new lens.

Fantasy plays a large part in the anticipatory saliva evoked by a good press release. In my mind, this was going to be a really useful lens: it would be the Nex system's answer to the venerable Canon 24-105mm F4, covering exactly the same FOV, with the same aperture, stabilisation too, and at the same price point. I imagined a rosy future with a very small and light travel kit that would cover nearly all my bases.

At the same time, Olympus announced the OM-D EM-1 and the new 12-40mm F2.8 Pro lens. So of course, being a confirmed gear nympho, I ordered all of the above. Again with the fantasy: the Oly gear would have a less good sensor (smaller, fewer pixels, less DR, for me the 'wrong' aspect ratio, worse ISO performance) and the Oly lens would have a less useful focal length but probably perform to a roughly similar IQ standard. But unlike the Nex, the combination would focus very quickly and, joy of joys for those of us with active canines, would be really well weather sealed.

So I had a plan: get both systems side by side and see which, overall, best meets my needs for all occasions (dog walking, inclement weather use, travel, day trips) when I don't want to carry a D800 system but might well need results that are good enough to sell.

I can't make that comparison yet: the EM-1 has arrived but the 12-40 is backordered. However, I was able to pick up the Sony Zeiss lens earlier this week and I can tell you now that our love affair was about as short as this opinion (I can't call it a full review, I gave up part way through...) will be. I found the optic about as disappointing as an ordinary kit lens, but at a multiple of the price. It also has quite notable purple fringing. And it doesn't feel like a grown up lens should.

I will link below to a gallery with some sample shots and you can draw your own conclusions. Mine are as follows:

At 16 and 24mm the edge performance (I didn't dare look into the corners) is not acceptable, to me, at either F4 or F5.6. It tightens a bit (but not enough) at F8 but of course by then the overall performance is starting to take a diffraction hit.

At 35 and 52mm F4 is still unsatisfactory at the edges, F5.6 might just satisfy an unfussy user and F8 is ditto diffracted.

At 70mm I gave up: it started to spot with rain and I packed the lens away in the sure knowledge that I wanted to return it, ASAP, and that it would therefore need to be unsullied by rain marks. Please forgive my seemingly cavalier attitude to the completion of this test but as far as I am concerned, however good the lens might prove to have been at 70mm it would not have earned a place in my bag. In any event, I have used it informally at that focal length and it failed to impress me. My lens might be a bad copy, and it seems to have a slight de-centering, but I have heard of other users having similar issues to those I have identified above.

The link to the images is here and they can all be downloaded at full resolution as 92% quality JPEGs. Let me explain them briefly. Everything is shot in RAW and developed in LR with clarity to +12 and sharpening of 50/0.7/70/20. The wharf side shots are at every major focal length (bar the 70mm as described above) and F4 thru F11. They were shot using wireless remote with OSS off on an Arca Cube/Gitzo CF rig, with manual focus on the distant railing, centre made in magnified manual live view and re-focussed at each focal length. The subsequent images are informative if more informally shot, all being handheld with OSS and AF. The distant hillside was shot at 16mm and F4 thru 8 with focus centrally on the far line of trees. The shots of the tower were the same focal length and aperture but with focus made using flexible spot, with the spot located over the tower itself and with no recompose. Again, please draw your own conclusions... Finally, a random forest shot to show the fringing, which I have left untreated. It isn't terrible, it isn't untreatable, but it is not mild and it is more than I expected and is again, like the overall performance of the lens, quite 'kit'.

So back the lens goes for refund and, ever the optimist, I await the arrival of the Oly 12-40 to see how it performs. I don't mind really: despite the extra focal length range of the Sony Zeiss offering, shooting it reminded me of why I never really enjoyed using the NEX-7 with its slow start and wake times and clunky interface. The EM-1 may not have quite such an impressive sensor but Lord is it made by photographers for photographers... and I will write more about that when I get the lens.

So what is the link to the announcement of the Sony A7 and A7R, you might ask?

I see it like this: I am hugely impressed by Sony sensors. I have an RX-1 and a D800e and they give the best results I have seen, period. So the idea of seeing such sensors in tiny, interchangeable lens bodies is tempting enough for me to have ordered the R variant. But I am aware of the potential fly in the Sony ointment  -  not enough glass, not soon enough and possibly not good enough (for me). And I think the E-Mount Sony Zeiss I discuss above is a warning sign. Frankly, IMHO Zeiss is ill-advised to let optics of this quality out of the door under their brand name but the fact that they have chosen to do so means they they are willing to, and might do so again. And guess what a key lens in the new FE range is? A Zeiss 24-70 F4 OSS** at a price slated to be very similar to that of the E mount lens I found so disappointing above. I will proceed, but with great caution and a firm grip on my sales receipt...

Aside from the new FE lens range co-announced with the A7 and R, there's the promise of an adaptor fest: vintage, legacy, loved lenses of almost any marque can be dusted off and mounted on either of the slimline siblings. And for quite a few people, that means M lenses.

Of course, the adaption of M lenses to other cameras has a fraught history: due to flange/sensor distance issues of some historical complexity, M lenses very often give ray angles to the edges and corners of non-M cameras that can mean colour and luminance shading and poor edge resolution, even on cropped sensors. The forums are littered with posts from people whose hopes have only been partially met as they gamely bolted M glass onto Nex cameras, MFT cameras, all sorts of cameras. It often just doesn't work well. Case in point, I tried my treasured M 50 Lux on the EM-1 yesterday and the edges are mush.

To the hopeful photographer it's always going to be different this time, though. The current narrative is that the new micro-lens array on the R will be enough to alleviate the problem. Forum Folk are currently gleeful at the prospect of a full-frame camera up to 36mp in resolution that not only takes M glass but has a built-in EVF and the luxury of a flexible focus point. And at a fraction of the price of an M240.

Don't believe it until you see it. It might happen, of course: never say never. But always accept that it has to be a maybe. 

Firstly, even the M240 struggles to deal with the colour shading issues, as I have documented in my series of reviews on this blog. Note: I have not yet tested the latest firmware to see how much of an improvement it offers in this area but other users report positively. So, bearing in mind that the Sony can't possibly have in-body lens detection and pre-processing for M lenses*, so keep your hopes reasonable, despite the promise of a helpful micro-lens array on sensor. Unless of course you want to run Cornerfix on every shot. I don't. 

Secondly, unlike the EM-1, the new Sonys don't offer any in-body stabilisation. Not a deal-killer but it would have been nice to use M lenses in that way.

Thirdly, I have proved to my own practical and theoretical satisfaction that the M240 RF is very often a better way of focussing M lenses than is the use of the EVF, magnified, peaked, whatever. The reasons for this are extremely complex and are laid out in my various reviews of the M240 and its lenses on this blog and on the piece on field curvature that I co-wrote with Roger Cicala but I will reproduce a very brief summary for those who don't want to read much more of my interminable prose...

Nearly all wide and standard focal length lenses have a degree of 'field curvature' which means that the plane of good focus is not, as you would hope, a thin or thick (depending on aperture) zone, exactly parallel to the sensor and with its near boundary parallel to its far boundary. Instead, depending on the particular lens, aperture and subject distance, it is generally curved, of varying thickness, and may be wavy in shape too.

Even when wide open but much more so when stopped down, there is more than one distance from the camera at which you can satisfactorily 'place' focus if you want the central subject to be sharp. But it is possible to place it such that the edges (and/or other parts of the frame) are not in good focus because they may not fall within the 'shape' of the field of good focus. 

Thus, when focussing with Live View, it is possible to 'see' good focus in magnified view, and to activate the 'shimmer', at a range of focus distances. Wide open and close up, that range can be as little as half a centimetre deep. Stopped down and at distance, it might might extend to several metres. Some of those focus distances might get all of the subject plane in focus and some quite possibly will not. But there will always be one exact focus distance that is optimal and, with a well calibrated rangefinder and very accurately machined lens focus cams, the system will find that distance. But with Live View, you have little chance of finding that distance unless you always focus wide open and then stop down to shoot - because Live View will encourage you to place the central subject in the middle of the field of focus, rather than in the 'best' place overall when the rest of the frame is considered.

The only exception to this general rule is that lenses which suffer from notable focus shift as they are stopped down will give better focus on the central subject when focussed using Live View if shot when stopped down. Also, certain types of subject pattern (anything with regular repeats) is easier to focus using Live View.

In other words, EVF focus is not a universal panacea for focussing M lenses. It is an extremely helpful option, in most cases will be very satisfactory, and on the A7 and A7R will be super-useful because they will (unlike the M240) offer the ability to select the focus point. Which means that for lenses with significant field curvature such as the 35 Lux FLE, you will have a better ability to focus peripheral subjects accurately. But for planar subjects shot stopped down, IMHO the M240 rangefinder is still the king.

If you do buy one of the Sonys and, on trying it with certain M lenses find that you are getting frames where planar subjects seem to wander in and out of focus there is an easy solution: focus wide open then stop down to shoot.

This may all sound like angels on pinheads but sometimes, to get a shot just right, you have to balance on a pinhead - and knowing how many angels you'll be sharing it with can really help you work out where to stand...

A final thought: I know for a fact that an awful lot of photographers have been waiting for a small high resolution full frame camera that, in exchange for those benefits, offers a very high quality EVF in place of a mirror and prism assembly. It is a trade off that large numbers of us are clearly willing to make. Sony, ever innovative and ever able to see and fill a niche, looks to have come up trumps. 

So what I have to say to CaNikon is this: remember IBM, think about Windows. Laurels can be surprisingly prickly.

* after I first published this piece I noticed this forum post regarding a Sony app that will allow just such correction profiles to be made and applied in camera, though it is not yet clear if they work for RAW files and there will in any event be some extra work and expense involved to add this capability. Like I said, never say never...

** Here is a link to a sample file from the A7R shot with the upcoming 24-70 F4 OSS at F5.6 though it doesn't say what focal length was used. The edges look fairly good, the corners less so... but not too bad either.

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