What Does The "S" Stand for in AFS?

OK, I'm at my wit's end. I've tried finding the answer to this question here, in

this forum, and on Google but run into roadblocks constantly. Can someone tell

me the answer to this question: What Does The "S" Stand for in AFS? And, why is

it better to have AFS lenses vs. simply AF lenses? BTW, I did look here:

http://kenrockwell.com/nikon/nikortek.htm

but it didn't answer my question.

Thanks.

Vincent

Sh...., you looked at the wrong places.

http://www.bythom.com/lensacronyms.htm

The "S" in AF-S stands for "silent wave", Nikon's terminology for an ultrasonic motor. It's not "coreless", as Thom Hogan's site said (sorry, Shun). The better AF-S lenses have a "ring" ultrasonic motor, where the motor is a hollow ring 50-70mm in diameter. All the lens's optics pass through the center of the ring. Lower cost AF-S lenses like the 18-70mm f3.5-4.5 have small ultrasonic motors that look like conventional motors, and turn a focusing gear.

As far as "why is it better to have AFS lenses"...

1) They focus nearly silently. No gears whining, no motor sounds. Even the ones that use gear motors have the ultrasonic motor turning much slower and with more torque than a conventional (electromagnetic) motor, so the low speeds and low gear ratios mean it's still pretty much silent.

2) They focus faster. The motor is exactly where it needs to be in the optical path, and it's sized to match the particular lens it's focusing. An in-camera motor needs drive shafts and linkages to get power to the lens. And like anything that's "one size fits all" it fits most people uncomfortably.

3) Full time manual focus override. You can turn a lens's focusing ring right after an AF-S lens has finished focusing to "touch up" the focus. You can turn the focusing ring while the AF-S lens is focusing to immediately take control from the camera's AF system, if you see the AF is doing something like going in the wrong direction or overshooting correct focus.

4) Better manual focus feel. If you like using both AF and MF, the AF-S lenses tend to feel better in manual focus operation than regular AF lenses do. There's more resistance and damping in the focus ring.

I like your answer Shun

Good one ...

So then AFD would = Auto Focus, Dummy/Dumb@$$? ;)

Here are some nice pictures of both the ring drive and the Full time manual mechanism (It's a canon lens, but Nikon's motor looks identical): http://tinyurl.com/3e22m

Here's Canon's Descriptions and pictures of both the Ring type drive and the smaller type: http://tinyurl.com/hf4xh