Originally posted by Nicolas06 between K3, A7 and D610... K3 is the least expensive and D610 provide the best picture quality in term of dynamic range, color deph and low light performance. It also provide you acces to fast AF lenses without needing an adapter that remove 0.3EV of light.
fast af? no
""In live view mode the D600 - like the D800 - uses contrast-detection autofocus, which allows for a continuous live view feed that doesn't black out during focus acquisition. The trade-off, however, is that the D600's contrast-detect AF is much slower than the phase detection AF the camera employs in its through-the-viewfinder shooting mode. In fact, like all current DSLRs, the D600's contrast-detection AF acquisition in live view is sluggish compared to most of the mirrorless cameras we've used. To be fair though, we imagine that for many D600 users, live view will be reserved primarily for critical focus applications like landscapes, still lifes and product photography, where maximum AF speed is less important than accuracy.
...Unlike Nikon's higher-end DSLRs though, the D600 does not offer live aperture control during live view viewing. When using live view, your lens is stopped down to the taking apertureat the moment live view is engaged. So if you want to shoot a scene at F8 for example, you're best off opening the aperture as wide as you can before entering live view, focussing at that aperture, then exiting live view and setting F8, and activating live view again to get the shot.
This is annoying, since it positively encourages focus errors until you realise what's going on. It's important to bear in mind that the D600's nearest competitor, the Canon EOS 6D, offers a more finessed live view experience, with the ability to turn exposure simulation on and off as well as aperture control/DOF preview in live view mode.
...The D600 is the first full-frame DSLR from Nikon that has not sported a variant of the 51-point AF system first seen in the D3 back in 2007. Instead it uses a tweaked version of the 39-point AF system introduced in the D7000. This system is perfectly capable but makes the D600 noticeably less versatile when focusing in poor light or in challenging conditions like sports, where its smaller, DX-format AF coverage could cause problems. That's the trade-off. If you need the ultimate in AF performance, save up for the more costly camera."
Nikon D600 In-Depth Review: Digital Photography Review
yes, the iso performance is impressive, but the functionality is obsolete, just like all dslrs.