Mirrorless… the one design to rule them all. The master of the full frame is undoubtedly Sony, however has it inadvertently introduced a short-lived shelf life with some in-built obsolescence?
Sony's Slow Burn
Sony, that behemoth of consumer manufacturers who brought us iconic designs such as the Walkman, have a strange camera heritage which includes the 1981 Mavica, the first digital stills video camera. For a company so wedded to consumers, it had long championed video cameras (anyone remember the Betamovie BMC-100P?) but was strangely silent (barring the Mavica range) when it came to stills. It wasn't until it acquired Minolta in 2006 that it's stills camera division was truly born. Minolta manufactured both cameras and lenses and was arguably at the technical leading edge from the 1970s onwards. In this sense they were a good match for Sony, although were late to the digital party, releasing their first DSLR (Maxxum 5D) in 2005 which used the 1980s A-mount for all its lenses. This is Sony's "standard" DSLR mount and can still be found on a few of its SLT cameras.
Sony followed the pivot to mirrorless that was led by Olympus and Panasonic in 2008 with their release of the Micro Four Thirds format. It's worth bearing in mind that this was an exciting time for mirrorless development and the requirement for new lens mounts. Sony released their first mirrorless camera in 2010 (NEX-3; APS-C), along with Nikon in 2011 (Nikon 1 V1; CX), Canon in 2012 (EOS M; APS-C), Fuji in 2012 (X-Pro1; APS-C), and Leica in 2014 (Leica T Typ701; FF). It's also worth remember that the Alpha 7 arrived in November 2013.
Has there ever been such a gold rush of lens mount announcements before or since? It makes me wonder about the nature of shifts in the camera industry. Consumer electronics has increasingly seen short iteration cycles of rapid development and product replacement. This is perhaps counter to traditional camera manufacturing, particularly for lenses which are intended for longevity. As a result, the market now operates on the basis of a rapid turnover of camera bodies and this may well be driving revenue. So why was there a sudden move to new mounts? Was the commercial success of Panasonic and Olympus a key reason or did the other manufacturers already have plans in the pipeline? Was it a case of herd mentality, with each manufacturer offering their own vision of what a mirrorless mount should offer? Remember that this was a period of rapid growth and large sales volumes, which almost certainly allowed for generous R&D budgets.
Sony, Nikon, and Canon were all relatively quick to market with new mounts and lens lineups, yet these were clearly consumer products. In particular, Nikon and Canon were clear that they didn't want to cannibalize their professional DSLR sales and that drove their mentality. It wasn't until Fuji's X-series and Sony's Alpha 7 that higher end mirrorless cameras came to market.
There are two primary design parameters for any new mount: mount-to-sensor distance (flange distance) and mount diameter. The flange distance is a result of the thickness of the camera which has to house all mechanical components. Principle among these is the viewfinder: in analogue cameras, manufacturers have used twin lens reflex and rangefinder designs, but settled upon the single-lens reflex. To accommodate the mirrorbox, the camera needed to be relatively thick, making the flange distance large: the Nikon F-mount (below) is 46.5 mm. By going mirrorless with an EVF, Nikon have reduced this to 16 mm with the Z-mount, whilst still incorporating an IBIS sensor.
The mount diameter needs to be at least as large as the sensor so that light can enter parallel to the optical axis. Leica's legendary M-mount is 40 mm which gives 2 mm of leeway on either side (it's also worth noting that the flange distance was a svelte 27.8 mm due to the rangefinder design). Making the mount diameter larger gives two benefits. Firstly, more light can enter the lens meaning, within design constraints, faster lenses can be manufactured. This is measured as the incidence angle, the angular deviation from the optical axis.The larger the value the better, although sensor microlenses become less efficient at extreme angles which can lead to vignetting.
Secondly, large mounts (by definition) result in larger orifices allowing significantly more space for optics, meaning manufacturers have greater latitude in their lens designs. The trade-off of bigger mounts is bigger (and heavier) lenses.
The combination of a larger mount diameter and shorter flange distance produces the largest incidence angles, but does any of this really matter? Well yes, because in the search for ever more exotic glass, manufacturers ultimately run up against optical physics and the constraints they impose. The flip side is that you can use the in-built advantage of a larger mount with more light, to produce simpler and cheaper lenses.
So how do the different mounts stack up? It's worth reviewing incidence angles for traditional DSLR mounts: the Nikon F is 12.14° (44/46.5 mm; mount diameter/flange distance), whilst the Canon EF is 16.8° (50.6/44 mm). This is one of the reasons why Canon shooters have often had a good lens selection. It also goes to show the constraints that the SLR specification places upon lens design.
So what about the new mounts? Here Nikon makes great play of a 41.2° (52/16 mm) incidence angle, in comparison to Canon's RF at 33.62° (50.6/20 mm). As a comparator, the MFT format runs at 32.5° (38/19.25 mm) which is perhaps what originally made other manufacturers sit up and listen: a significantly smaller body, significantly smaller lenses, yet relatively fast glass (not withstanding the effect of the crop factor).
And what about the other mounts? The Leica L is 33.13° (48.8/19 mm) and Fuji X is 35.3° (40.7/17.7 mm). Which brings us back to Sony, the first to the punch with a full frame mirrorless mount which has an incidence angle of 28.6° (43.6/18mm). Except it wasn't designed for full frame mirrorless but its NEX series of APS-C format cameras and camcorders. This raises the question as to the design motivations of Sony when it first developed the E-mount. Was it to terminate the Minolta product line and split their offerings in to an APS-C mirrorless range that could support both stills cameras and camcorders, along with a "professional" A-mount SLT line? If you calculate the incidence angle of the E-mount for an APS-C sensor then it is a much more forward looking 37.9°.
So did Sony intend to produce a full frame mirrorless camera or was it a result of the success of its NEX range and some Sony labs product experimentation? Was there always a plan to disrupt the DSLR market with mirrorless or did they fortuitously expand at a time of DSLR decline? Certainly, pursuing the mirrorless full frame format when camera sales were so high seems a risky strategy in comparison to Nikon and Canon, yet the inroads they have made in to the market have subsequently been significant.
Of course the performance of the E mount is still significantly better than comparable DSLRs and back in 2013 gave them the flexibility to produce competitive quality lenses. However that advantage has now flipped back to Canon and Nikon (and to a certain extent the L-Mount Alliance) with the release of the RF and Z mounts which are designed from the ground up for full frame mirrorless, with Nikon arguably the most aggressive in its pursuit of competitive advantage. Canon is also no stranger to mount development: over the period of Nikon's F-mount, they have had the R, FL, FD, and EF mounts which didn't seem to hinder the success of the brand.
Has Nikon built a lens mount that provides users with the option of exotic glass (such as the 58 mm f/0.95 Noct), whilst giving the flexibility for a wide range of affordable lens designs from third party suppliers? Or has it encumbered itself with another great design that will simply be superseded by another manufacturer in a few years time? Has Sony shot itself in the foot by sticking with the E mount and relinquishing the mirrorless advantage it once had? The willingness of photographers to change brands suggest the "stickiness" of remaining with one manufacturer may be short lived. Or will we see Sony, and then Canon, iterate over mount designs to constantly improve their optical offerings?
Do you think Sony should change mounts?