Originally posted by Pål Jensen This is like saying a Pentax LX have no reach advantage over a Pentax 67 when using the same film.
Of course APS has an dvantage over D800. If you remove that advantage the D800 is not an FF camera anylonger and hence the comparison becomes meaningless.
I don't quite agree. Of course, if you're a birder, and almost exclusively shoot with long lenses, the D800 is probably a complete waste of money and bulk if you're fine with the K-5. But if you only use long lenses occasionally, the situation is different.
Suppose, for instance, that Pentax makes our dream camera, a K-5-like camera, not much larger, and with good viewfinder support for APS-C lenses. Further, suppose that it has the 36mp sensor so it's roughly equivalent to the K-5 when cropping.
Mostly I shoot with shorter lenses, but occasionally I use the DA55-300. I wouldn't even dream of replacing that lens with an equivalent FF-covering lens, so
if I buy the hypothetical camera (the "k-1"), I would probably use it with a couple of new wide-angle to normal lenses, I would still use the DA70, which gives pretty nice results on FF, and I would use it
cropped with the DA55-300. End results: I would get better results (in theory...) for most of my photography, and equivalent results when I use the long zoom.