Originally posted by northcoastgreg When the Nikon D3 first came out, the distance between FF and APS-C really did seem quite significant, and predictions of the imminent demise of APS-C were not uncommon. Since then, APS-C has closed the gap and cameras like the Pentax K-5 and Nikon D7000 or now so good that many of us no longer care about the IQ advantages of FF.
Well, current APS-C cameras approached old FF cameras in high ISO's. However look at resolution. I took example from photozone.de Nikkor 85mm f/1.8 D lens tests:
On 10 Mpix APS-C camera resolution @f/5.6 is 2188
On 16 Mpix APS-C camera resolution @f/5.6 is 2716
On 12 Mpix FF camera resolution @f/5.6 is 3779.
I am not good at optics and can't explain why, however it is solid evidence, that FF cameras, even with lower resolution sensors, are able to capture more resolution than their APS-C counterparts.
Also don't forget that K-5, D7000 are relatively very new cameras with excellent sensors. FF cameras still use old sensors. Therefore the gap is narrowed. When new FF cameras, using the same sensor technology, will be released late this year/next year, the gap again will be widened a lot and we will say again "Wow, my K-5's ISO800 is worse than ISO6400 on this camera!"