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With few exceptions, you're going to be much better off only buying Nikkor lenses. Stay away from Sigma and Tamron. The D5000 doesn't have a focus motor, so only buy lenses AF-S, AF-I, or G lenses if you want auto focus. I'll assume you already have the mediocre kit lens (18-55mm). Next you should invest in a fast prime. The Nikkor 35mm f/1.8G AF-S or the Nikkor 50mm f/1.8G AF-S are both excellent lenses.
Sigma has a 70-300 zoom lens that is comparible with the Nikon F55. It costs around $150.
There are several online sources for reviews of the Nikon 70 300. Amazon has customer reviews from people who have bought and used the product. Technology bloggers will show the pros and cons of the Nikon 70 300.
Yes, the sigma is a good lens for the money. One cannot expect professional result with this chepo lens but for an enthusiast it will serve the purpose.
Yes--but only in manual mode, so you'll have to set your own aperture and shutter speed.
The Nikon 70 300 VR is a telephoto zoom lense. The Nikon 70 300 VR can be purchased at many retailers including Amazon, Wal Mart, NikonUSA and Best Buy.
No http://www.amazon.com/Sigma-100-300-F4-5-6-7-Nikon-Manual/dp/B002CJ03TU
i would advise a 18 55 lens and a 18 70 lens. They are good beginner lenses in low light but i would advise an 18 135, 18 200, 70 300
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Yes
If all you can have is one lens, pick a wide-angle zoom with an 85mm setting, and the largest aperture you can afford. If you can have two, get...oh, a 28-80 or 24-105 as your wide lens, and either an 80-200 or 100-300 as your long one. I like the 100-300.