I don't know how many people remember all the discussions way back in the mists of the distant past when Canon ABANDONED their long time, FD, bayonet lock lens mount and put all their chips and bets on the new EOS EF lens mount. It was a crazy brave thing to do when they were locked in what was basically a two way sales contest between Canon and Nikon. But do you remember all the white papers and marketing rationales for this cataclysmic change? No? Let me do a refresh...
The old Canon mount was close to the size of the Nikon mount and both worked very well as long as super fast lenses were not required. Remember that back in the mid-century film days an f2.8 lens was a routine and daily user. People generally accepted that lenses performed best at two or three stops down from wide open so speed wasn't the obsession it is today and photographers were happy to get great images at a relatively low cost per lens. Photojournalists and others who worked in low light pushed camera makers to get faster lenses but mostly because having more light pouring into the dimmer DSLR viewfinders meant it would be easier to achieve quicker and more accurate focusing; even if they eventually stopped down to f5.6 to take the photographs.
With Canon and Nikon competing head to head,
and with Nikon having a longer tenure in the market, Canon decided that the key to remaining competitive, or pulling ahead, might lie in making a series of faster lenses that also performed well closer to wide open. Faster lenses that might even be usable near their new, super-wide maximum apertures. But the small diameter of the existing lens mount one their FD series cameras made designing these fast lenses (especially wide angles) a very, very tough engineering challenge. Early attempts at fast glass and small lens mount diameters made for lenses with high vignetting and too many other optical compromises.
Canon, seeing the rise of autofocus realized that it was the last real opportunity to change the lens mounts and not lose out on their market share entirely. They envisioned the new EF lens mount as being much bigger and much better suited to all sorts of esoteric autofocus lens designs. Stuff like the legendary 50mm f1.0 EF, the 85mm f1.1.2 EF and faster wide angle lenses than had been seen in the SLR markets before. It also eliminated the expensive and troublesome mechanical lens linkages for aperture sensing and stop down. The faithful FD mount owners bitched and moaned but eventually either fell in line or switched systems. But it was the change to the much better engineering solution that gave Canon a 20 year leg up over Nikon when it came to optimizing lens designs for modern (give me more speed! Give me more wide angles!) consumer demands. The bigger mount was/is a better solution and offers companies a much more flexible platform. It also made the progression to using full frame sensors much easier.
Now, as Nikon comes to grips with the idea that mirrorless cameras really might be the next move forward in consumer demand they seem (according to the rumors) to have adapted the same philosophy Canon used decades ago. If all the stuff is going to change anyway then this must the the "jumping off time" in which changing to a much superior mount will provide the least damage to market share and the brand while providing the most leverage in making tasty, fun optical products in the near, and distant, future. The predicted "Z" mount is going to be BIG. Really BIG.
But what does this have to do with "power house" Sony and their current rampaging market share gains in the full frame space? That's really the question for all three full frame camera makers going forward. If Nikon really sees enough advantage in changing mounts to take the risk of pissing off millions of embedded Nikon F mount users then those advantages have to be pretty damn HUGE.
So, Sony has been killing it in the FF mirrorless space. People seem to love the smaller bodies. And it's tough to design and build a smaller body with a big lens mount. People love EVFs, and frankly, who doesn't? And Sony has really good video, right? Well........now that the D850 has been launched Nikon has delivered a huge upgrade in the quality and flexibility of their video features and the image quality difference between the two brands, at least at the flagship level, is now more a matter of taste than any contest with a clear winner.
But let's circle back to that Sony Nex lens mount. It's a mount that was originally designed for consumer, cropped frame cameras. Its forté was helping to keep systems small by keeping Nex lenses small and cute. The bigger, Alpha mount, used on the a900, a850, a99, etc. was intended to be their professional mount for full frame cameras but the engineering intent got destroyed by listening too closely to the ill-informed demands of an army of "give me mini-cameras" consumers. They wanted a full frame system that was as close in size as Sony could make it to the existing Nex APS-C cameras. And mob demand has dictated now three whole generations of Sony A7x camera design. The mount in an A7Riii is barely big enough to fit a full frame sensor and requires much magic mechanical and optical engineering to deliver an image edge to edge onto the sensor. The worst of the geometric compromises are dealt with by in-camera software hocus-pocus.
BUT...Sony have rushed countless cameras to market and positioned themselves as the presumptive future leader in the full frame space....with a lens mount that is clearly not up to the task of delivering the kinds of fast and compromise-free lenses that consumers (and professionals) will, no doubt, demand. They have the automobile equivalent of a fixed 15 inch wheel rim size in a market in which people are recently demanding 20 inch rims. In fact, the rush to implement a small camera with a small diameter lens mount may have unwittingly doomed Sony to a dead end system which will require a wholesale redesign of lenses and bodies in the not too distant future. Not a very promising proposition for the legions that are currently switching systems away from Nikon and Canon to Sony.
My one disclaimer is that the new Nikon is not yet here so we can't really measure the lens mount and prove its engineering advantage. But, imagine you traded in all your Nikon/Canon gear and bought Sony only to find that you might never get super fast lenses for the system or that you may have to dump it all for salvage value in short order as Sony comes to grips with the need for a "new and improved" mount earlier than later... I think I know how I would feel.
If Sony maintains the small mount it gives even advertising tone deaf Nikon a huge marketing advantage and one even Nikon might be smart enough to leverage. At least with the change of the Nikon mount to one that is bigger and shallower Nikon is more or less guaranteeing that adapters will fit and older lenses with smaller mount diameters will be able to be adapted. That's got to make a transition for Nikon users easier.
Me? Oh, I keep thinking Canon is the real grown-up in the room. They just keeping making stuff and selling it to hordes and hordes of advanced amateurs, sports photographers, moms with cameras, wedding photographers, baby photographers and, well, the main stream users. Think "larger numbers." I haven't used one but I'm betting that the 5Dmk4 is a nicely mature and eminently capable photograph generating machine. Probably Canon is the company for people that don't give a rat's ass about the usual photo drama. Maybe that's why the review site hipsters are loathe to spread some market joy in Canon's direction. Reminds them too much of their mom's Buick and they'd rather drive a Vespa.
I love all the intrigue about "earthshaking" camera changes and introductions. I talked about it at my attorney's law firm yesterday. Nobody knew what the hell I was talking about and even fewer cared. I'll probably end up getting billed for that discussion. Ah well.