Lens for Nikon D3100? - 1

I really want a good lens for portraits for my Nikon D3100 and I really want a shallow depth of field, so I was thinking either a:

Nikkor 50mm f/1.2
Nikkor 35mm f/1.4
Nikkor 50mm f/1.8

Or should I get a macro lens? I really want crisp photos and the current lens, a Nikkor 18-55mm f/3.5, is not sharp enough.

Any good ideas?

Added (1). Really? So what about a Sigma 70-300 mm. F4-5.6 macro?

Macro lens offers shallowest depth of field. If I were to choose from the three, f/1.2 is my choice, because aperture affects depth of field, and the lower the number, the shallower.
I would actually buy a zoom lens, like 18-200, or 70-300, since the more you zoom, the shallower your depth of field.

If you can't get sharp enough photos with your kit lens, I don't think you can get it with any other lens. It's how you set it up - camera, lens and light.

With portraits, f/1.8 is enough, f/1.4 is great and f/1.2 is heaven. F/1.2 will be so shallow you won't get that overall crispiness you are looking for.

Macro lenses are for shooting at very close distances to make small objects seem large. Their maximum aperture sizes aren't as large as what you have listed and will not perform as much (DOF-wise) as you would wish for portraits.

The 50mm f/1.8 should be the most economical with the f/1.4 the best choice for value.

Justin is right and wrong at the same time. Macro lenses get extremely shallow depth of field, yes - but only if the subject is very, very close to the lens (during actual macro use). At portrait distances (which you asked for) that effect doesn't occur. A macro lens will have the exactly same depth of field as any other lens with the same focal length and aperture then.

I'd strike the 50mm/1.2 from the list. It's an ancient Ai-s lens and wouldn't even meter on your camera, and of course it'd be manual focus only. That's not worth the hassle, and f/1.2 is very exotic anyway.

Get yourself a nice 50mm/1.8G AF-S or 50mm/1.4G AF-S. Make sure that you get the AF-S versions, as the older AF ones wouldn't autofocus.

A 35mm prime would be too wide for portraits, forcing you to get close and thus causing an unfavorable perspective. Think of big noses.

I'd stay away from that Sigma lens. While you can also get shallow DoF by using long focal lengths, you'd be getting a slow unstabilized telephoto lens.It'll be hard to obtain sufficient shutter speeds with it without a tripod in anything but bright sunlight or flash.

I would get the Nikon 50mm f/1.8G. For macro, 40 or 60mm macro would be great.

And the Sigma 70-300mm isn't a macro lens, no zoom can do that, it's just false marketing that many beginners believe.

Here's a DSLR Buying Guide- http://www.the-dslr-photographer.com/2009/11/which-dslr-to-buy/