Couple of Nikon Lens questions

[Gen.Ben]

Im just getting into DSLR's and was wondering....

there is AF and AF-S... The AF-S lenses are alot more expensive. Why? What are the differences?

I am getting a 18-70mm that comes with a D70 for normal shooting. I want another lens that has greater zoom for sport photos. I've been looking at a couple such as a 18-135mm, 70-300mm. The 18-135 has more zoom than the 70-300 but The 70-300 is also more, why is that?

 

[Craddosk]

THe difference between the AF and AF-S lenses is that the AF-S lenses contain an autofocus motor in them. It yields faster focus times, and permits autofocusing on the D40/D40x/D60. The internal motor on the lens is the only difference.

The 70-300 is more, from my understanding, because it zooms to a higher range, and is of higher build quality. If your getting the 18-70, I would say going for the 70-300. Getting an 18-135 and a 18-70 would be redundant.

 

[Garbz]

Large zoom range is not correlated to cost. Just look at those sub $200 Olympus point and shoot cameras with 10x optical zoom.

Quality and zoom range is normally correlated. The 18-200mm is less sharp than the 18-70mm Nikkor lens. This is not always the case though. Cost and aperture are normally correlated too. The 17-55 f/2.8 is $2500 here, the 18-55 f/3.5-5.6 is $400.

This all depends on how hard it is to manufacture the glass needed to get quality pictures at certain specifications (zooming with a wide aperture is hard).

I should also mention that AF-S is a silent wave motor. They use a very different technology to control the lens than the motor in the camera and the focus is 2-3x faster than a good body with a good motor, if that is a selling point to you.