Serial Number: Laser engraved in bottom rear of metal barrel. This makes for highly legible silver on black. Legitimate USA products are prefixed by "US."
Made in: Japan.
Optics
Overall, the 24-70mm is weakest at 24mm. It's at its best from 35-70mm, where it's easily the sharpest and highest performance lens I tested in this comparison.
Focus Accuracy
Focus seems AOK on my D40.
On my D200, autofocus focuses too closely at 24mm. At 24mm wide open, I get far better results using what we do in television studio production, which is to zoom into 70mm, lock focus, and zoom back out. On a D200 at defaults in AF-S mode, zoom to 70mm, press the shutter halfway, and hold it ot hold focus while you zoom back out to 24mm.
AF is fine from 35-70mm, even on my D200.
Sharpness
Duh, of course it's sharp. Why do otherwise reasonable people spend so much time worrying about such an insignificant issue, especially for a state-of-the-art Nikkor lens and especially when so few people ever print bigger than 13 x 19" (30 x 50 cm)?
Sharpness comes from a photographer's vision. It doesn't come the correct choice of lenses. All lenses are about as sharp at f/8, where we usually use them. The differences I'll reveal below are applicable only at large apertures. Lenses get sharper as stopped down, until about f/8, beyond which diffraction sets in.
Just for fun, I shot off the 24-70mm against everything but a 28-70mm AFS (I don't have one of those handy, but will). When my D3 arrives, I'll do that, too.
When I say 28-70mm AF-D, I mean the 1990's compact zoom, not the f/2.8 AFS. I can add more lenses as I stop down, since fewer lenses open up to f/2.8.
Lenses Compared (only some at each focal length):
17-35mm AF-S
18-35mm AF-D
18-55mm AF-S II
Ugly 24mm f/2.8 pre-AI
24mm f/2.8 AF-D
24-120mm f/3.5-5.6 AF-D "Streetsweeper"
24-120mm f/3.5-5.6 VR
28mm f/2.0 AI-s
28mm f/2.8 AI-s
28-70mm f/3.5-4.5 AF-D (not the f/2.8 AF-s)
28-80mm f/3.3-5.6 G (nasty silver-painted version)
35-70mm f/2.8 AF-D
35mm f/2.8 Nikkor-S (AI-converted)
50mm f/1.8 AF-D (China)
50mm f/1.4 AF-D (China)
Of course there always are shot-to shot variations, but here's a rough idea of what I saw on my D200. The sharpness differences I see are at a 44" (1.1m) print size seen from a foot or two away on my monitor. These differences would be hard to see in 13 x 19" (30 x 50cm) prints, and you'd need to get out a magnifier to see anything in 8 x 12" (25 x 30cm) prints.
At 24mm
At 24mm and f/2.8, I discovered that the focus is consistently in front of the subject on my D200, so it's not sharp enough for testing at 24mm. (It's perfect on my
D300 and D40; I just didn't use them at first.)
24mm is the 24-70mm lens' weakest setting. Every other lens was sharper due to the focus issue.
When I figured out a work-around, which is to AF at 70mm and zoom back out (which is cheating), here's what I see:
f/2.8: The 24-70mm is the clear winner. The 17-35mm is second, the 24mm f/2.8 AF-D third, and the ancient, ugly 24mm AI-conversion last.
f/4: The newest 24-70mm AFS wins again. Second place is tied among the 24-120mm AF-D "Streetsweeper," 18-35mm AF-D, 17-35mm AF-S, 24mm f/2.8 AF-D and 24-120mm VR. THe hocky-puck 24mm AI Conversion is worst, but not mby much. The 24-70mm stands alone.
f/5.6 - f/8: At f/5.6 to f/8 the lenses are more or less as sharp as one another. The issue at moderate apertures is lateral color fringing. The 24-120mm VR, 17-35mm AFS, 18-35mm AF-D have none. The 24-120mm AF-D has some. THe 24-70mm AF-S, 24mm AF-D and the beater 24mm AI conversion have visible lateral color, at least at the crazy magnifications I'm using. THe 24-70mm tends to be a little sharper than some other lenses, but has a little more lateral color, so it's a toss up among them.
At 28mm
At 28mm the 24-70mm is OK, but not a clear winner from some residual AF error on my D200. Here's what I see, shooting them fairly against one another:
f/2.8: The 28mm f/2.8 AI-s is sharpest all over. The 24-70mm is the same as the 28mm f/2.0 AI-s, when all are shot at f/2.8.
f/4: The 24-70mm is as sharp as the 28mm f/2.0 AI-s. The 28mm f/2.8 AI-s is better, and lo and behold, the best is the small 28-70mm f/3.5-4.5 AF-D I bought used from Adorama for $100.
f/5.6: At f/5.6 and smaller they are all equally sharp. They all also have the same amount of lateral color fringing, except for the small 28-70mm f/3.5-4.5 AF-D which has none.
If I cheat and focus the 24-70 AFS at 70mm and zoom back out, which imprioves it slightly, and also throw three more lenses into the mix that weren't included above:
f/2.8: Now the 24-70 beats all. The 28mm f/2.8 AI-s and 28mm f/1.4 AF-D are close seconds. The 17-35mm AF-S and 28mm f/2.0 AI-s are worse.
f/4: THe 24-70mm wins again. THe 28-70mm AF-D is second. THe 28mm f/2.8 AI-s, 28mm f/2.0 AI-s, 18-35mm AF-D and 28mm f/1.4 AF-D are tied for third. The 17-35mm AFS and 28-80mm G are last.
f/5.6: THere isn't much difference at f/5.6. THe 24-70mm wins. The 28-70mm AF-d and 28mm f/1.4 A-D is second. THe two AI-s 28mm lenses, the 18-55mm AF-s kit lens, and the 18-35mm are all third, but not by far. The 17-35mm AF-S is last. None of these lenses have any significant lateral color fringing.
At 35mm
At 35mm, the 24-70mm has finally hooked up and is easily the best of the lenses I tested at 35mm.
f/2.8: The 24-70mm is clearly the best, sharp and devoid of lateral color even wide open. The 17-35mm AF-S is a close second. The 35-70mm f/2.8 AF is third and has some lateral color. The 1972 35mm Nikkor-S (AI converted) was clearly the worst.
f/4: The 24-70mm is clearly much better than the 28-80mm G, 18-35mm AF-D, 28-70mm AF-D and the 35mm Nikkor-S. The 17-35mm AF-S and 35-70mm f/2.8 AF-D are a close seconds.
f/5.6 - f/8: The sharpness differences lessen, although the 24-70mm still wins. The 35-70mm f/2.8 AF-D, 18-55mm AF-S kit lens, 17-35mm AF-S, 18-35mm AF-D and 28-70mm AF-D and 35mm Nikkor-S are similar. The 28-80G is the loser.
As the softer lenses have sharpened up, lateral color is obvious in the 35-70mm f/2.8 AF-D and somewhat in the 35mm Nikkor-S, 18-35mm and 17-35mm. . There is no lateral color in the 24-70mm, 28-80mm G, 28-70 AF-D or 18-55mm AF-S.
At 50mm
Golly, at 50mm the 24-70mm also is the clear winner, even better than the fixed 50mm f/1.4 AF-D and 50mm f/1.8 AF-D!
f/2.8: The 24-70mm is clearly the sharpest. The 50mm f/1.8 AF-D is a far second, and the 35-70mm f/2.8 AF-D and 50mm f/1.4 AF-D are the worst.
f/4: The 24-70mm wins again. The 28-70mm AF-D is tied with the 50mm f/1.8 and 28-80mm G for second. The 35-70mm f/2.8 AF-D loses.
f/5.6: Similar to before with the differences less obvious. The 50mm f/1.8 and 28-70mm AF-D are close seconds. All the others, as well as the 24-120mm VR, are all tied for last.
At 70mm
The 24-70mm wins again, although I only compared it to mid range zooms, no pro tele zooms and no fixed lenses.
f/2.8: The 24-70mm is sharper, contrastier and has much less lateral color fringes than the 35-70mm f/2.8.
f/4: The 24-70mm wins, with the 35-780m a closer second. The 28-70mm AF-D is a far last.
f/5.6: 24-70mm wins. 35-70mm is second. 28-70mm AF-D and 24-120mm VR tied for third. The cheap est 28-80mm G loses.
Lateral Color Fringing
Lateral color fringing is minimal at 24mm.
It's gone from 28mm through 70mm.
This is as I measured on a D3; it will be less on a DX camera (see Crop Factor).
Nano Crystal Coating
Nano Crystal Coating is a new kind of coating to reduce flare and ghosts. There is only one internal surface with this coating.
This is the big gold "N" on the barrel. To you and I, coatings are just one tiny part of a far more complex issue. This is Nikon's new marketing letter to push lenses on the innocent. Nikon has invented a new letter about every 7 years. "N" is merely incremental, as AF-D is from AF or AI-s is from AI. Don't stay up at night worrying about it.
A lens' ghost, flare and contrast performance depend on many, many many factors. It depends more on the wisdom of the lens designer than a coating on one surface of one element. The other zillion surfaces have Nikon's traditionally excellent Super Integrated Multicoating (SIC).
Flare and Ghosts
You really have to be doing something stupid to see any ghosts. For all reasonable photo situations, including those with the sun in the image, the ghosts fall outside film or digital's dynamic range.
There can be a couple of spots if you deliberately try to create them. I wouldn't worry about this. It's better than the 35-70mm f/2.8 AF.
Distortion
Distortion is stronger than I had hoped at 24mm, otherwise, no surprises. Shoot it at about 30mm and the distortion goes away.
Luckily, for the one shot in a thousand where you might care, it's easy to correct completely in Photoshop CS2's lens distortion filter. There is no weird waviness as is common with other complex aspherical lenses. Distortion, if any is visible, is one simple constant-radius curve.
The Nikon 24-70mm has strong barrel distortion at 24mm, and pincushion elsewhere. Use these numbers in Photoshop CS2's lens distortion filter to rectify it. 