http://www.nikonchat.com/nikkor-wide-angle/

Do I feel if I can buy a Sigma or Tamron lens for my Nikon?
I know at some level, you get what you pay for, but the high cost of Nikkor lenses I have been looking for alternatives. "I can get something comparable in quality to Nikon lenses if I go with one of the better-off brands such as Tamron or Sigma? I suspect that paying the premium brand above and beyond the legitimate costs of equipment. In particular I would like a fast (f2.8 or so) wide-angle zoom is not a variable aperture of 3.5 -5 max, without loss of $ 1,200 – $ 1,400.
The Tamron 17-50mm f/2.8 XR Di II has a maximum aperture of f/2.8 fixed has been reviewed quite well. It is designed specifically for digital sensors, so do not attempt to use this in a movie or full format sensor cameras. (You did not say exactly what type of camera you have.) Http: / / www.photozone.de/8Reviews/lenses/tamron_1750_28_nikon/ http://www.bobatkins.com/photography/reviews/tamron_17-50_review.html http://www.the-digital-picture.com/Reviews/Tamron-17-50mm-f-2.8-XR-Di-II-Lens-Review.aspx index.htm
Nikon COOLPIX S640