Sony mirrorless

[pez]

Actually, the Pentax DA 40mm Ltd. is auto fucus and employs quickshift as well...

 

[Garbz]

Not necessarily.... although I don't know all the technicalities.

True when you take into account all the extra crap (focus, VR, features etc). Lens design will play a big role in the size of the lens, but physics will ultimately dictate how big a lens needs to be, and sensor size, and sensor distance are key. Less light needs to be captured to cover a smaller area, which is why my sister's point and shoot has an f/2.8 lens the size of my thumbnail

The practical downside is image quality specifically for depth of field as we know. However noise is not so much of a concern as it is a technical design issue. A 10mpx micro 4/3rds sensor would have a larger pixel size than a Canon 7D. Olympus just needs to lift their sensor design game and you'd end up with a very very capable yet tiny camera.