After I bought my first SLR camera (actually a DSLR - the Nikon D40) four years ago, I was eager to obtain a telephoto lens since I'm anti-social and don't like to get too close to my subjects. Actually, I sometimes like to pretend I'm a nature photographer and wild animals would never let me get close enough with the 18-55mm kit lens that came with the camera. So I picked up Nikon's 70-300mm AF-S lens in April 2007 and have been very happy with its performance. The only problem is that it only goes down to 70mm, and it seems like I'm forever switching lenses, which is quite a nuisance juggling lens caps and trying to keep dust from intruding into the innards of the camera body and lenses.
So, when I recently upgraded my D40 to a new D3100, I thought I would also get myself Nikon's highly-regarded 18-200mm lens at the same time. This one lens covers almost the same range as my other two lenses combined, with the obvious advantage that I never have to swap out lenses. Now, I had read several reviews prior to buying the 18-200, and I was well warned that while it was an extremely convenient lens, it came at the cost of some image quality over superior shorter range lenses. I even saw a side-by-side comparison (with a 55-200 lens, not a 70-300) from Camera Labs which showed poor corner sharpness, but generally acceptable center sharpness, at least to my eyes.
Now, I am not really a critical photographer and I certainly don't make money taking pictures - it's just a personal hobby. However, I was quite alarmed at the poor showing of center sharpness of the 18-200mm lens at 200mm vs my 70-300mm at the same focal length in my own unscientific test. See for yourself below. Though my backyard in the winter may not be as aesthetically pleasing as other picturesque samples, this mossy rock provides a lot of edges and surface detail for an excellent sharpness comparison:
The above photo is from my new Nikon AF-S 18-200mm VRII lens at 200mm.
This picture is from my Nikon 70-300mm AF-S VR lens at 200mm. Notice how much sharper the details are in the are of the moss on the rock, and the surrounding leaves.
So, I was originally intending to sell my 70-300 lens to help pay for the new, ultra-convenient 18-200 lens, but now I'm not so sure. Though I'm not a professional photographer, I'd hate to lose the relative sharpness of this lens because, well, its better than the 18-200 lens. I had hoped that the 18-200 would at least be acceptable to my eyes, but this comparison is telling me a different story. I'm going to have to think about this before I put my 70-300 up for sale. Bummer.