There is a lot of chatter lately about Canon and Nikon tardiness in the mirrorless world. On one side, Canon seeked feedback from their user about what they want in a pro mirrorless camera. On the other side, Nikon is announcing a full frame mirrorless camera with a new lens mount dubbed “Z-mount”. In both sides there is one topic that seems to come back into the discussion: the camera should be directly compatible with the SLR mount (EF for Canon, F for Nikon). While it is clearly understandable why users would want that, let’s explain on why it is not a good idea, and why the mount adapter is the best compromise — compromise that Canon made for the EOS-M.
A lens mount is defined by a certain number of attributes ; flange distance is the one that matters here.
The flange distance or register distance is the distance between the lens mount ring on the camera body and the focal plane (the surface of the sensor or the film). It is a fixed dimension for the lens mount.
On an SLR camera, you have the mirror box between the lens and the sensor, defining a minimum flange distance, while a mirrorless doesn’t have the mirror box. This is why in general a mirrorless camera has a much shorter flange distance even with a similar sensor size.
For example, Sony E-Mount is 18mm while Sony A-Mount (former Minolta SLR) is 44.5mm, as Canon EF-M is 18mm while Canon EF and EF-S are 44mm. In both cases the flange on SLR mount is more than twice as large as on the mirrorless.
What would a DSLR mount do on a mirrorless system? It would increase the thickness of the body in way that the camera wouldn’t be that much more compact. The real example is Pentax mirrorless Pentax K-01. With a flange distance of 45.46mm for the K-Mount, the camera is bulkier than it should with a thickness (depth) of 59mm. In comparison, the Canon EOS-M100 is 35mm thick (deep) as it uses the EF-M mount, designed for mirrorless.
That’s why using a DSLR mount for a mirrorless system, meant to be more compact, isn’t a good design choice. Offering an adapter that support all the features of their DSLR mount is, on the other hand, the best compromise that a camera maker can do, almost equivalent to the practicality of using native mount, but the advantage of the size: the extra bulk only comes if you need it.
My opinion, without having seen it. The new mount and the small sensor are two things that could hinder the camera success. The sensor, “CX size”, smaller than the one of m4/3, but still bigger than the one of the Pentax Q, make it more difficult to contain the noise at high ISO. I haven’t see samples yet to make myself an opinion. Also the new mount means that the lens will be specific to the system. I do believe Nikon could have benefited from joining the m4/3 gang instead and could have introduced Nikon lenses to the mix for the variety. It is one of the reason m4/3 cameras are popular.
On the other hand, the GPS accessory, while a bit overpriced, seems to be a welcome addition that virtually no other maker has. It is not Nikon’s first attempt.
For the mess that is the Nikon F mount. Next time someone tells you Nikon never changed the mount, get them to check this one. At least Canon moved from FD to EF in a non compatible way. This does not lower the other qualities that Nikon gear have.
The tragedy in Japan has made the current DSLR market a scary place, making this a perfect opportunity to get (back) into film.
Their list (in alphabetical order):
Canon EOS 1N
Mamiya 645 Pro
It seems to cover all the bases from medium format, compact to reusing lenses from your DSLR. But the most awkward in the list is the FM10 as I think they should have recommended an older model instead, one solidly built. Also notably absent are TLR or 35mm rangefinders like a Bessa.
What is interesting to see is that Ricoh is still in the same line of products with their Ricoh GR-Digital: highly praised compact camera.