Originally posted by philbaum I know a professional photographer in town who's selling his D800 and lenses due to its effects on a previously injured leg.
LOL, Did I mention I got camera elbow / bursitis from carrying a Speed Graphic
There's another article that puts things in perspective,
LumoLabs -- True reasons for Full Frame -- Whitepaper
Basically: where equivalences exist, the two formats are equivalent. The trick is APS-C doesn't always have the aperture speeds to be equivalent to the full frame brother. Whether or not that is a critical, crucial difference is up to each one of us. Same way that it is up to each of us whether a fish eye or an ultra long lens makes sense for what we do.
To a good extent, digital doesn't suffer from miniaturization as much as film -- though theoretically this may not be so, but in practice 35mm gives much better results than 1/2 frame, and 120 6x7 or 6x9 better still, and so on. In part this has to do with sensor vs film technology. And a good portion has to do with simple physical laws: the smaller you cram your 100 lpm or whatever your goal is, the more every piece has to resolve and avoid aberration. Hence it is easier to get certain quality from a large scale camera than a small scale one.
But of course not everything is equal, and there are other considerations - portability, flexibility, health of one's joints, cost, speed, fun, and so on. There are very few photographs that rely solely on maximum image quality for effectiveness - usually it's a matter of 'good enough' quality for the purpose, or interest 'despite' or 'because of' imperfection.
ps. I bought a D600 for the larger view finder (evf's not being quite there yet, and optical ones are subject to size) mainly, and to mount lower cost legacy glass at its designed FOV. I don't think of the camera as otherwise superior to a low end Pentax APS-C.