One of the great things about shooting Nikon is that, if you have a little money to throw around, they produce some really excellent optics.
For Full Frame Sensors (FX)
Nikkor 24-70 f/2.8G ED
Nikon’s relatively new 24-70 f/2.8G is a very fine lens, probably better than Canon’s older model in overall resolution and certainly when it comes to field curvature. The resolution is extraordinarily high at all apertures and all focal lengths in the center, and at around f/5.6, the border image quality is quite good as well, a very typical pattern for large aperture, wide-angle zooms.
The Downsides: Chromatic aberration is somewhat high, and there is significant barrel distortion at the wide end, though both can generally be corrected in post. And of course, the lens costs about $1900.
Nikkor 70-200 f/2.8 G ED VR II
This newer version of Nikon’s fast, pro-grade 70-200mm lens has corrected the problems that worried so many of us with the original version: the vignetting on a full frame sensor is well controlled, and the borders are sharper when shooting wide open. Indeed, the resolution of this lens is excellent in the center of the image regardless of aperture, and from about f/5.6 and smaller, it is very even across the entire frame. The focusing speed and build quality are excellent, as you’d expect with a lens of this caliber. Overall, this is a top-notch lens, though I prefer Canon’s.
The Downsides: Due to the internal focusing mechanism, the lens actually has significantly lower magnification when focusing close-up; when set to 200mm, the lens performs more like a 135mm at it’s minimum focusing distance; whether this will be a problem for your shooting style is up to you to determine. And as usual, Nikon’s premium lenses carry premium prices, though in this case, the price is similar to Canon’s offering.