With this push/foray into high-grade, fast zoom lenses compatible with 35mm sensors, we have to finally understand that mirrorless is not just about size. The size advantage we’re used to associating with mirrorless is all but gone with lenses like the G-Master trio: 24-70mm f/2.8 (note that it lacks image stabilization, probably to maintain sane size/weight—similar move to what Fuji did with the 16-55mm f/2.8, though Sony now has IBIS to back it up), 85mm f/1.4, and especially the 70-200mm f/2.8.
With the mirror box gone, what we have is basically a DSLR in Live View mode. But with the EVF-equipped cameras, we’re not restricted to just the rear screen—we can use the same Live View in the eye-level viewfinder. This is the difference between DSLR and mirrorless cameras, not size. Any other difference is specific to the comparison of certain models, and cannot be a generalization for the types of cameras.
As I see it, mirrorless cameras don’t have to replace the DSLRs—they just bring another view of the world, literally. It’s actually to the benefit of all of us if some manufacturers still produce DSLRs, as we can still have the choice between an optical viewfinder and an electronic one, as the photographer sees fit.
Of course, as technology progresses, electronic viewfinders will only get better and better. They will be able to show even greater dynamic range, amplify light levels in low light even more (to make it easier to compose the shot in such low light that you can hardly see anything with the naked eye), and have such smooth transitions and fast refresh times that you won’t even notice it’s an electronic display. Blackout times will become so minimal, that you’ll be able to shoot fast bursts without missing a beat. But still, nothing can travel faster than the speed of light, so the optical viewfinder should always have its place.
So far, those who prefer the constant Live View in the eye-level viewfinder had to make some compromises if they’re used to DSLRs. At the very beginning, when Micro Four Thirds was the only mirrorless system, you had to compromise on the sensor size. Then came APS-C mirrorless cameras, which gave at least some DSLR users the same sensor size they were used to, but lenses were lacking. Then the lens lineup for APS-C started filling in with faster and better lenses. At the same time, Sony gave full-frame DSLR users the same sensor size they were used to, but again lacking in lenses. Well, that lack of lenses is now gone for a lot of those users.
Obviously, Sony isn’t revolutionizing anything with these lenses. Canon and Nikon have had their versions of them for a long time now. This is just Sony doing what they’re supposed to do: filling out the FE lens lineup with lenses that professional photographers would use. And these three lenses—especially the 24-70 and 70-200—are without a doubt lenses that professionals would use on occasions that call for them, and a lot of occasions call for those types of lenses.
They will be very good lenses. They better be, considering how expensive they are, and also how big they are: the 24-70 costs as much as the Nikon VR and more than the Canon L II, and it’s bigger and heavier than the Canon; the 85mm f/1.4 is more expensive than the Nikon, and is over 25% heavier; the 70-200 will be expensive—it’s made up of 32 elements!
This is the direction I see mirrorless going: please highly demanding professionals first, worry about size and weight later. Give those D5/1D-X and D810/5D-S/5D-III a comparable camera with Live View in the viewfinder, and surround it with the lenses they need. Well, that’s at least where the Sony α7/FE and, to a slightly lesser extent, Fuji X systems are going; Micro Four Thirds is still about a balance that’s tilted a lot more towards portability and lightweight. And the Sony APS-C system isn’t going anywhere: it’s just Sony’s playground for ideas before they make it into α7 bodies.