Some Thoughts on Nikon's Upcoming Mirrorless Announcement
Nikon has been increasingly hinting at their imminent full-frame mirrorless announcement for some time now and even have a countdown clock on their website showing when it will occur. Hint: it's set for August 23.
Exact details will have to wait until the announcement on the 23rd, but consensus seems to be that the new cameras will feature a larger Z-mount as apposed to the current SLR standard F-mount. And yes, there likely will be more than one new camera announced. Sensor size is expected to the same as the current FX format. In a teaser for the expected announcement, Nikon recognizes that they have "built a legacy of incredible cameras and lenses around the iconic F Mount." With this new mirrorless line, they state that they are "aiming for new, unprecedented heights" while building on their existing "technology and DNA." It should be possible to mount at least most F-mount lenses on these new cameras by means of an adapter.
Notably, even though the lens mount will be larger, the camera body itself is expected to be considerably smaller, based on the current full-frame Nikon D850 body for comparison. This smaller size makes sense since one of the primary constraints today is providing the necessary room to fit the reflex mirror that defines an SLR camera. The body of any Single Lens Reflex camera is basically a large, open box through which the mirror swings up and back down with every click of the shutter. It's this mirror that reflects the image produced by the lens upward through the pentaprism to the viewfinder. When the shutter fires, the mirror moves up and out of the way, allowing light to strike the image sensor. Mirrorless cameras obviously don't need room for the mechanical movement of a mirror, and thus mirrorless camera bodies can be smaller. The viewfinder in a mirrorless camera is fully electronic, using the data from the same CMOS sensor that records the image.
As a slight digression, shouldn't DLSR cameras be called "mirrored" cameras and mirrorless cameras simply be "cameras?" It does seem strange to define a type of camera by what it lacks than by what it has that sets it apart. Of course, all this might have come out with a more logical naming convention were it not for the precedence of history. Sometimes, you're just stuck with the terminology you've got and have to go forward from there. Years from now, photographers will have as much difficulty explaining why their camera is called mirrorless and indeed just what mirrors ever had to do with cameras as we do today speaking in terms of keeping things parallel to the "film plane" and doing our post-capture image work in a digital "darkroom." Anyway, a rose by any other name I suppose. Don't get me started on why we use an "unsharp mask" to sharpen images.
Anyway, contrary to what some folks have suggested, this won't be Nikon's first foray into producing mirrorless cameras. Nikon introduced their line of interchangeable lens Nikon 1 cameras back in 2011 featuring the smaller, CX sensor. As an interesting coincidence, Nikon just last month announced that they were discontinuing the Nikon 1 camera line. So far as I can find, the last Nikon 1 models came out in 2015 which is years ago in digital years. OK, it was years ago in calendar years, but you get my point. I feel certain Nikon internally made a decision to change course with their digital strategy long before they officially told any of us.
Now we get to the question of what to make of Nikon's upcoming announcement.
Sony has pretty much had the full-frame mirrorless market to itself with the Alpha line of cameras. Canon is said to have two full-frame mirrorless bodies in development. Nikon clearly didn't want to be left out in the cold. The future continues to bring new advances, and now that Sony has more than proven the viability of a mirrorless full-frame market, the rest was inevitable. When you get right down to it, having a mirror in a camera is a crazy idea whose days are finally numbered. With a film SLR camera, a reflex mirror and optical viewfinder were the only possible option. With a digital body, those old limitations no longer apply.
No one needs to sell their existing lenses and buy new ones to go mirrorless. The rumored lens adapter should work fairly well. Apart from its obvious functions regarding mount diameter and electrical connection interfaces, all it really should need to be is a fancy extension tube. Lacking a mirror, the new Nikon body should be skinnier than exiting bodies, making the film plane (sorry, I mean "digital plane") closer to the lens mount. Pushing the lens out a bit should let a regular Nikon DSLR lens achieve focus on the sensor in its new position. It's not clear to me right now whether such an adapter would even require any glass elements.
One could easily ask why Nikon would need to change the lens mount at all? For many years, Nikon has bragged that they have kept the F-mount the same, even when Canon abandoned their old FD-mount and moved to their now standard EF-mount in 1987, a key component of their EOS system. The older FD-mount was even smaller in diameter than Nikon's F-mount. Anyone who's ever casually checked out the current Canon EOS line can confirm that the mount on EF-lenses is much larger diameter than Nikon's F. But increasingly since then, Nikon has been blaming engineering difficulties on the complexity of fitting ever more electronics for features such as silent wave motors and image stabilization in such a small mount. Moving the image sensor forward due to the removal of the mirror made it possible to change the mount diameter while still supporting older lenses via this adapter. I doubt there could have been any better way for Nikon to increase the lens mount diameter. Any other way would have antagonized their existing users even more. Ask a longtime Canon shooter how pissed off they were when Canon abandoned their legacy FD-mount.
I think this larger mount might help facilitate other advances as well. It stands to reason that a native Z-mount lens should be able to produce a larger diameter image circle. This could provide the means for the future use of a larger sensor in order to increase resolution without pushing pixel densities ever higher. Nikon DSLR cameras already rival the resolution of medium format, and this change could allow Nikon to raise their game even further.
Even with the existing FX sensor, a larger image circle could still have advantages. Nikon has long found it more difficult to produce tilt/shift lenses than Canon seems to. Focus stacking can sometimes be used now to address the challenge of extreme depth of field in a different way, but a tilt lens makes the same thing possible in a single shot.
Only time will tell how this new mirrorless thing will work out for Nikon and for Nikon users. We won't really know until we see how all this turns out in the rearview ... er, ... mirror.