What are the differences between these lenses?

Links:
http://www.nikonusa.com/...F1.8D.html

http://www.nikonusa.com/...F1.8G.html

They both are 50mm lenses w/ f1.8 and autofocus. So what is the difference between these lenses other than the second one being more expensive. I'm going to be using this lens with a D3100 and they both say they support DX mount. Also, the first one looks like it has a metal enclosure.So, what's the difference?

Essentially the same, the previous answer is not correct about focusing, but that is not the primary issue. The G lens means that it does not have an aperture ring, this means the camera has to control it. With the other one, it means that a manual only camera can work it, but G lenses require the camera to control it.

It all honesty if you have a modern camera G lenses are fine, and they (nikon) can save a little bit of hardware cost by not including the aperture ring.

AF means auto focus, so both will do that just fine, its the metering that is possibly compromised.

EDIT: AF-S means Auto-Focus - Silent wave motor.

The silent wave motor simply means the lens will focus itself through the output of the camera.

Really I mean come on SWM tech is 1998, if you think you can buy a D3100 that doesn't focus itself is a laugh with any AF lens. Where do you people come from?

look at it this way, there's no aperture ring on a AF-S G lens, because the camera does it. Its why AF but non-g lenses need it as it can't control the Aperture. The user controls the aperture, which is why I said the metering is not involved with non- AF-S lenses.

EDIT: According to Nikon's website a D lens will not be focused by a D3100, so i eat crow, but that is really not the point, the question was what is the difference between the two lenses. The AF-S has 7 pieces of glass while the other has 6, that is an important fact.

Score, Taylor 1, cedykamen 0.

The aperture ring is irrelavent with modern Nikon DSLR cameras, as if you have one on the lens, it needs to be locked anyway. You control the aperture via the command dial(s) on G and all other Nikon autofocus lenses.

AF means the lens uses the screw-drive system connected to the camera body's internal autofocus motor.

AF-S means the lens has an internal autofocus motor and uses electronic connections to drive the focusing mechanism.

The newer Nikon 50mm AF-S f/1.8 G lens is an AF-S model, and is the only Nikon 50mm f/1.8 lens that will autofocus with your D3100 and all other entry level Nikons.
http://kenrockwell.com/...-f18-g.htm
http://www.kenrockwell.com/...018daf.htm

Here's a full list of lenses that will mount, meter, and autofocus with your camera. Please note that the lens Taylor and I are describing is listed.

As for the "full metal enclosure", both 50mm lens have a metal frame with high-grade plastics used in their construction. Both have the same basic metal mounts for a long-lasting solid connection.
http://en.wikipedia.org/...cus_motors

p.s. Our so-called "pro" posted this question. Some "pro".

The AF version will not autofocus with your camera. Get the AF-S one. Update - cedykamen is absolutely clueless. Another update - Dude, you're clueless. All AF-S and G lenses are also D lenses. D does not indicate presence of an aperture ring or lack of a built-in autofocus motor.