I've used them all, briefly on multiple occasions. I've used the X-mount most so here's my opinion:
I've you want a die hard opinion on the tech specs just look at DPreview what I'll give is a brief notion of my experience.
I consider the X-Pro1 to be one of the nicest camera's to be out there, it's not without flaws, which makes sense consider it was the first product of a completely new system, but that things that are important to me all work very bloody well.
The system itself is excellent, X-mount is still young and there aren't many lenses out, but they are all great, in terms of build quality and amazing optical quality. There isn't a 'dog'. Also there's an adapter for M lenses and there are adapters for Canon, Nikon, Minolta etc..(no AF of course) so you can experiment with a lot of current and legacy lenses.
The camera is great, it's build incredibly well, it doesn't only feel solid it is solid, engraving is actually engraving not just a scratch filled in with a micron layer of paint. It feels like a camera that can out last you, it almost feels Leica like.
It's also inconspicuous, silent, it doesn't scare people like a big SLR. It's not as small as an OM-D but if you are considering carrying an OM-D this is a small step-up. unlike the big step down to compacts or the big step up to DSLRs.
Image quality is good, really good and pictures come out great in jpeg, I hardly felt I needed to shoot in raw.
But most importantly, it feels inspiring, it may sound vague but I get the same feeling when I walk around with my Nikon F, it's just a really nice camera.
Now go to DPreview and pixelpeek.
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