I have a nikon 50mm 1.8 lens what would be the next great portrait lens i should buy?

I don't know maybe something with a little bit more reach then the 50mm. A lens with sharp pics and decent quality.

Added (1). Sorry i didn't say it is a nikon d3100:)

Http://www.kenrockwell.com/tech/portrait-lenses.htm

Since you did not tell us what camera you are using it is hard to say.

The 50 mm lens is too short for shooting portraits using a full frame camera like the Nikon 35 mm SLR's, D700, D3 or D4

The 50 mm lens when used on a cropped sensor like all the other Nikon dSLR cameras it is the perfect focal length for shooting portraits. Another option would be the 60 mm f/2.8 macro lens

I shoot with a Canon, but… Focal length is focal length and Canon and Nikon have comparable lenses. When I'm unsure of which new glass will meet my needs/wants, I narrow my choices and then rent some for a week(end) to help me decide which to buy.

Depending on the distance to the subject, I use a 50mm f/1.4, an 85mm f/1.8, and a 70-200 f/2.8L for headshots/portraits.

This may help you determine the right lens type for your camera… Http://imaging.nikon.com/lineup/dslr/d3100/compatibility02.htm

I would suggest saving the nifty fifty for those shots where you know the focal lenght is perfect and/or you need the fast aperture. For portrait, I'd suggest a decent quality zoom lens like a 28-135mm for instance.

Prime lenses are actually more for experienced photographers that know what lens they need for a given situation. Zoom lenses will allow you to change focal length on the fly. Focal lenght is used more to control perspective than it is to zoom into the subject.

The links in the "sources" below will give you all the details on this and could very well be the most important things you ever read in photography. As you will learn from these articles, photos are as much about perspective and surrounding as they are the subject you are shooting.

Just don't forget to come back and give me my "best answer": P

A little bit more reach would translate to longer focal length. Get something with more mm like a 75mm or 80mm perhaps. Here, learn all about lenses to make the right decision.

http://keerok-photography.blogspot.com/2011/05/lenses-so-many-of-them-there-is-no-best.html

Let's assume your budget is fairly low, you have those two

Nikon 85mm f1.8D $460. This model won't focus automatically on your camera.

Nikon 85mm f1.8G $499. This one is fairly new on the market.