> >>for all kinds of photography, astronomy, landscape, >>panoramics, travel, flat field copying, etc. My need for >the >>accurate focus is shooting ballroom dancers under less >than >>ideal lighting, fast motion. >> > >Hate to say this, but your D600 was the ideal camera - there >is going to be no comparison with a DX sensor based camera >above ISO 1600, though the D7100 looks pretty nice and is the >most like the D600 from a control and capability perspective.
Greetings! Though I as yet have "only" a D5200, based on my research into the D7100, I tend to agree with David that the D7100 is an excellent body that would be best served with fast glass, especially in your possibly low-light ballroom settings. I expect with the right exposure and technique, you'll achieve some excellent images! That said, FF would probably be even better, though obviously more costly. Good luck! Steve