I bought this lens after reading a good review about it. Previously I had the nikon 18-105 lens which I had bought as a kit lens for the nikon D90 body. When I saw the good review I thought it might be a good idea to switch to a wider range zoom lens which - as the review said - was better than the 18-105 lens. So I sold my 18-105 lens and bought this 18-200 one.
I have to say that it is a pretty good lens. It is compact for such a big zoom range and optically it is decent. It is actually good if you think about the compromises which go into creating such a big range zoom. It feels pretty solid and has a metal mount. One of the reasons I didn't like the 18-105 was its plastic mount.
At 18mm wide open the corners tend to get quite fuzzy. At f5.6 they become good and at f8 they are quite sharp. at 18mm I usually shoot landscape, so I don't really need the f3,5 setting. Well I used it once and wasn't very happy with the result. I had to crop the edges of the picture to make i usable. the 18-105 didn't have this problem. at 18mm f3,5 the corners were quite good.
Image stabilization or VR as nikon calls it is pretty good. On this lens it is actually the VRII. It helps you get away without a tripod when taking pictures in low light. Again the VR is actually useful only when shooting static things. When shooting portraits in low light it cannot compensate for a moving subject. I was pretty happy with the VR of the 18-105 lens and couldn't notice any big difference between it and the VRII of the 18-200 lens. But I never took the time to thoroughly test this feature. Here are some handheld pictures taken in low light with the 18-200 lens.
Is the 200mm end of this lens really a 200mm focal length? Well, I also own the 180mm f2,8 nikon lens, and while taking pictures of a bird one day I noticed that the 180mm lens brought the subject closer to the camera than did the 200mm end of the 18-200. I didn't have any explanation for this at the time and was a little disappointed. In the meantime I made some tests, did some research and found the answer.
The focal distance of a lens is measured at infinity.
Underneath you can see a comparison. the images are not cropped and are taken with a tripod from the same place (except the last one). As you can see in the first two samples the 180mm lens frames the view slightly wider. This means that the 200mm end of the 18-200 lens is somewhere around 200.
|nikon 180 f2,8|
|nikon 18-200 @ 200|
The next two images are taken from the minimum focusing distance of the 180mm lens which is somewhere around 1,8 meters. As you can see the 18-200 one frames the subject wider. In fact it looks like it has a focal length of around 110mm. What happens is that on the 180 prime lens, when focusing on a close subject the front lens gets pushed out, making the barrel of the lens longer. On the other side, the 18-200 has IF (internal focusing). This means that the barrel of the lens remains the same length while focusing and when focusing on a close subject an inner group of lens gets pulled back relative to the front lens. This has the effect of reducing the focal length when focusing on subjects close to the camera.
|nikon 180 f2,8 min focus distance|
|nikon 18-200 @ 200 2m focus distance|
This feature of the 18-200 IF lets you get very close to the subject even at 200mm. You can see this in the picture below ,which is taken at the minimal focusing distance of the 18-200 lens at 200. So some people say that they don't mind taking a few steps toward the subject to frame it closer. And this is true as long as you take pictures of flowers for example. But if you're out taking pictures of birds or butterflies you would probably want to bring them close to the camera without having to get closer to them and scaring them off.
|nikon 18-200 @ 200 min focus distance|
Here and here are some more pictures taken with this lens.