Needing Wanting Needing a new wide angle lens, I picked up a 20mm f/2.8D lens. Not being able to justify the cost of a 24 1.4 or the size/weight/cost of the 14-24 2.8, I decided on the 20. The few reviews I've even found of the lens mounted on a D800 have not been particularly positive. But after talking to a friend who has one that they shoot on the same camera, I decided to go for it anyway. I'm quite pleased so far. I did have to do some fairly heavy-handed AF fine tuning (-15, which is really kind of a lot). But once I found the sweet spot, it works pretty well so far.
The sharpness, which I'm fairly sure isn't up to a $2000 lens, is pretty good. At f/2.8 the center is reasonably sharp in the center and even up to 2/3 frame. The edges at 2.8 are soft. Keep your subject near the middle if you're going to shoot wide open. As you stop down, it gets slightly sharper in the middle and a good bit sharper at the edges, though at no point does it get super sharp at the edges. f/5.6 is about the best overall. I'd feel perfectly comfortable making large prints with shots from this lens on my D800.
Sharpness of the 20mm AF-D on a D800 at f/2.8. Focus is on the leaf in the center of the frame. Again, reasonably sharp at center. Not sharp in corners.
It shows some pretty bad chromatic aberration (including some orange aberrations, which I thought was odd), but not nearly as bad as I expected and certainly mostly correctable in post-processing. And when I say bad, it's not that bad. I shoot with a 70-300mm 4.5-5.6 VR for my tele. That has some serious CA problems, especially from 200-300. This 20mm has nowhere near as bad CA as that one. The barrel distortion is pretty strong, but it's a wide-angle lens, so good (unless I were shooting architecture, which I'm not). It has heavy vignetting (probably about 2 stops in the corners), but it fades evenly to the middle of the frame, so it's not noticeable in most real-world shooting. And the D800 has such a wide dynamic range, that you can reverse the vignetting with no loss of detail in the edges (which don't have much detail anyway:).
An interesting thing that I didn't expect is that it has a bit stronger contrast than any of the other lenses I've worked with on this camera or any other. I'm not sure how I feel about it yet.
All this is just first impressions based on shooting about a hundred random shots. I'll discuss more when I have had time to play some more.
Bluriness is my fault (holding lazily) and the water's fault, not the lens.
UPDATE: I added a couple random shots. What good is a review without images?