Let me explain why a) full-frame is important, and b) mirrorless is important and c) a rangefinder/viewfinder is important.
The answer to 'what's the best camera you can own?' is 'the camera that's round your neck at all times, ready to shoot.' You can indeed buy a Nikon D4S or Canon 1D X, but these beasts weigh in at a kilo and a half (body only) and you don't want that plus a full-frame lens (weighing another half-kilo) stressing your musculoskeletal system all day long.
A smaller, DX-sensored DSLR like my wonderful Nikon D3200 weighs just 650g with a universal 18-55mm zoom lens. Yes, you can carry this around your neck all day long without feeling it. But the difference in quality between a full-frame (FX) and the smaller DX format is noticeable.
How can you marry the quality of a full-frame sensor with the weight advantage of DX format? Dispense with the mirror that's required to give you through-the-lens view of your subject. A rangefinder allows you to focus precisely, like in the early days of 35mm photography, when Leica and Contax ruled the world. No mirror means shorter flange-to-sensor distance, which means the lenses can be smaller and lighter and still have big apertures.
Without a rangefinder (or simple viewfinder) in a mirrorless camera, you are dependent on the screen to compose. For us ageing folk who need reading glasses, this is a big problem. With a DSLR or rangefinder camera, you set the right diopters in the window through which you compose, and you can do so without having to put on glasses. With just a screen to compose from, this is impossible, taking away the spontaneity that's so necessary when snapping. I don't want to have to think...
"Hmm... photo opportunity. Take out and put on reading glasses, switch on camera, look at the back of my camera with arms outstretched, composing on a little screen at a distance of 20-30cm... snap..." No. I want to lift the camera to my eye, compose, snap.
So - how would my dream mirrorless Nikon look?
|Nikon S3D digital rangefinder, with manual Nikkor 50mm f1.4 lens.Indeed, any Nikon S-mount lens would fit. Contax and Kiev lenses too. And with an adaptor, Nikon F-mount lenses would work just as well (only heavier and bulkier).|
|Nikon S3D digital rangefinder - 3-inch LCD screen, standard, familiar, intuitive Nikon DSLR controls on the back. Rangefinder window would have diopter settings.|
|Nikon S3D digital rangefinder body showing full-size FX-format CCD sensor|
|Nikon S3D digital rangefinder top-plate - thumb-wheel for manual focus|
This time two year ago:
Longer, lighter lens
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New engine on the coal train
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High time to leave the car at home
This time five years ago:
The answer to urban commuting
This time eight years ago:
Far away across the fields