AF–S VR DX Zoom–Nikkor 18–200mm f/3.5–5.6G IF–ED lens review
Designed for Nikon and Fuji digital SLRs with APS–C sized sensors and announced on 1 November 2005, this lens has become so popular that as of November 2006 it is still either backordered or can only be purchased at significantly higher prices than MSRP (for instance, USD925 vs. USD750 in China). The reason for this popularity is very simple—the lens boasts a huge range of focal lengths (equivalent to 28–300mm in 35mm format) and yet, in spite of this and its prosumer class, produces image quality that is surprisingly good. On top of this, the lens also incorporates state–of–the–art technologies that further improve its usability and functionality, namely AF–S focusing and second generation vibration reduction system (VR II). Sounds intriguing? Then read on to find out where the lens performs as expected and where it comes short of delivering.
If necessary, you can find simple explanations of the terms below here.
AF–S and VR
Both of these features, without a doubt, are brilliant and work well. One, however, should be aware of the fact that they are no panacea as there are many factors at play. Silent wave motor (AF–S) certainly improves focusing speed; overall speed and precision of autofocus, however, are also massively dependent on the camera's autofocus module and, especially in low ambient light, the lens' maximum aperture. Vibration reduction (VR), on the other hand, while indeed allowing shooting at slower shutter speeds, does not completely substitute for good high ISO performance and fast apertures.
The 18–200 zoom is a very slow lens—at 70 mm its maximum aperture is only f/5 and in the 105–200mm range it is even slower (f/5.6). This does not seem to impact autofocus if/when the lens is mounted on a Nikon D200 and in relatively bright ambient light; on a Nikon D70s and in dim light (as, for example, here), however, autofocus is quite sluggish and far from hunt–free despite the lens having the AF–S feature.
The slow maximum aperture of f/5.6 will also inevitably impose using slower shutter speeds at any given ISO setting, which might induce the problem of camera shake. It can be effectively resolved by using VR, which is perfect if you only take pictures of still objects. VR, however, does not eliminate subject movement and one has to boost ISO to compensate for the slow speed of the lens and freeze action. This is a typical example of what VR does and what it will not do—the buildings are tack sharp but the cars are blurred:
Nikon D70s, ISO800, 1/15 and f/4.8 at 24mm, hand–held with VR on
Finally, there is the issue of depth of field—VR or no VR, at f/5.6 it is pretty much impossible to produce sufficiently shallow DOF. This, of course, might be inconsequential for some photographers; I, however, would suggest looking at other options if you like pictures with beautiful out–of–focus background.
Build quality and handling
Build quality of this lens is more or less on par with, say, the 18–70 zoom or mid–range digital camera bodies (D70s, et al), which is quite adequate for photo gear of this class. When zoomed to 200mm, however, the lens is quite long (about 16.8 cm) and feels somewhat vulnerable because of the length. This, combined with the fact that it is subject to "zoom creep" (see below), does not inspire confidence whatsoever.
The lens has been broadly reported as being "small". It probably is not huge considering the range of focal lengths but, on an absolute basis, it is by no means tiny—for one thing, it is noticeably larger than the 18–70DX zoom, which I consider as the perfect companion to my Nikon D70s in terms of bulk and weight. Its size is perfectly acceptable if this is the only lens that you intend to own; using more than one optic, though, I personally find that it is a bit too much for casual/walk–around use and, overall, a bit too little for more serious purposes.
Handling of the lens is far from perfect. Zoom ring is rather stiff and, moreover, the way it operates is funky at best. First, it is impossible to zoom from 18mm to 200mm in one go without taking one's hand off the ring (well, it is possible but you would have to move your left shoulder, arm and hand in a very peculiar way), which is a major inconvenience. Second, zoom ring movement has different degree of looseness/stiffness at different focal lengths and, furthermore, depending on whether you are zooming in or out, as well as if you are shooting horizontally or the lens is pointed down. When shooting horizontally and zooming in from 18mm to 200mm the ring gradually feels tougher with the maximum stiffness being between 70mm and 135mm, which then is followed by an abrupt looseness towards 200mm; when zooming out from 200mm to 18mm, it is somewhat loose at first but then becomes stiffer from 70mm onwards. When the lens is pointed down, zooming in is very, very loose (to the extent that the lens extends all by itself, i.e. "creeps", when, for instance, your camera is hanging off your shoulder); zooming out, on the other hand, is extremely stiff. All of this is obvious when you casually handle the lens and really gets to you if you use it continuously and intensely for a couple of hours.
On my 6MP Nikon D70s the lens is adequately sharp throughout the whole range of focal lengths and aperture settings. Wide–open, one might detect slight softness in the corners but the difference would be invisible in prints; and of course, as with any lens, diffraction kicks in at small apertures. This disparity in sharpness will be somewhat more accentuated on 10MP cameras (D80 and D200) yet I do not envision it being pronounced enough to cause noticeable deterioration of image quality of real–life photographs. As we are unlikely to see higher pixel counts on APS–C sized sensors, this lens seems future–proof in terms of sharpness (and no, I did not forget about the D2X—but do not tell me that this lens mounted on a D2X is your preferred combination ).
In the age of digital SLRs importance (or, depending on how you look at it, insignificance) of vignetting depends on whether you shoot RAW or JPG. The choice between RAW and JPG, however, is an almost religious debate as there are proponents of both approaches who will readily give you quite a few compelling reasons to support either of the formats. I personally shoot only RAW and for RAW shooters vignetting is almost of no consequence as it can be removed (or, indeed, added, if one's creative intent dictates so) in a RAW converter (if you use Adobe Camera Raw, go to Lens > Vignetting). Those who favour JPG, on the other hand, have to live with whatever is written into JPG files by the camera at the point of shooting.
The good news for those who use this zoom and shoot JPG, however, is that vignetting is surprisingly well–controlled. The aberration is practically gone at the following apertures (note that I am being quite picky here):
18mm (max aperture: f/3.5)—f/8
24mm (max aperture: f/3.8)—f/4.5
35mm (max aperture: f/4.2)—f/5
50mm (max aperture: f/4.8)—f/5.6
70mm (max aperture: f/5)—f/8
135mm (max aperture: f/5.6)—f/10
200mm (max aperture: f/5.6)—f/10
As you can see, vignetting is least pronounced in the 24mm–50mm range of focal lengths. Here it is also much more gradual and thus almost unnoticeable in real–life prints.
Given the lens' range of focal lengths distortion is not controlled badly at all, too. The only caveat is that at the wide end its signature is of a complex type and cannot be corrected in a straightforward (or any at all?) manner in post–processing. This is bad news for serious photographers but a good thing for normal people who do not go out of their way looking for distortion. If complexity of the aberration was a conscious choice/preferred compromise of Nikon engineers it is very clear why so—this is a prosumer lens and for most "civilians" complex distortion of lesser magnitude is more desirable than more obvious to the eye simple distortion.
You will need the following approximate numbers in Photoshop to correct the aberration (go to Filter > Distort > Lens Correction > Remove Distortion; I am posting these numbers not because you will not be able to figure them out by yourself—this, indeed, is very simple—but to give you a rough idea of relative degree of the aberration as well as its behaviour at different focal length settings):
18mm: complex barrel–dominated; correction numbers in PS: +6.4 at about 1 meter and +2.5 at infinity; note, though, that straight lines running near frame edge will remain a bit wavy.
24mm: still a tiny bit complex (but much less so than at 18mm) but of the pincushion–dominated type; correction numbers in PS: -0.5 at about 1 meter and -2.5 at infinity.
From 24mm on the lens shows simple pincushion distortion and correction numbers in PS are as follows: -2.5/-3 at 35mm, -3.0/-3.5 at 50mm, -2.5/-3 at 70mm, -1.5/-2.0 at 135mm and -1.0/-2.0 at 250mm (all numbers are at about 1m/infinity).
Other performance factors
I did not properly examine bokeh because, first, the lens is too slow to be purposefully used for producing shallow depth of field and, second, my impression has been that in in real–life photographs with significant out–of–focus areas bokeh is generally neutral and, where it is not particularly nice, not alarmingly so. Chromatic aberration is controlled reasonably well but does show its ugly face around sharp contrasty edges in the corners, especially at the long end. I did not encounter any problems with flare even though the lens has no less than 16 glass elements (most modern zooms are generally good in this respect, though); if, however, you have concerns about possible contrast degradation, use the lens hood supplied with the lens.
In the final analysis, what we get essentially is an ample range of focal lengths and a very good optical performance in a lens barrel that neither handles well nor inspires confidence. The AF–S focusing and VR make the optic more attractive and partly compensate for the lens' slowness but, unfortunately, come at a very steep price. At the end of the day, in my opinion, this is one of those relatively rare occasions when the line of desirability of a product is clearly drawn by its price (I normally buy gear that I need no matter how expensive it is (within reason, of course) and never buy stuff I deem unnecessary no matter how cheap it is). In case of the AF–S VR DX Zoom–Nikkor 18–200mm f/3.5–5.6G IF–ED lens, I would have bought one long ago had it been selling for around USD700. USD925? Thanks, but no thanks.