http://www.nikonchat.com/nikkor-80-200-f4/

Nikon Lens Pro, which is better sigma, nikkor?
this might sound like a stupid question, but I have and I have to try to find a Nikon Sigma 80-200 f2.8 or the "Bigman" 50-500 f4 I was thinking about the F2 is better for low light, but the thing 50-500 wouldnt be so bad:)
If you have Nikon camera, it is best to buy only Nikon lenses. However, if you can not afford the prices, there is nothing wrong with buying another brand like Sigma. I bought a Sigma 105mm macro lens. I love it. I think it has excellent crisp pictures. The f2.8 would be better for low light. It is a fast lens. But in the same direction to reach the final 500mm would be good too. In the end, we must ask, what are you using these lenses? Wildlife … many of them. Some kind of photography that has the 500mm would be the best decision. Or 200 mm to be fine. There is a difference between 200 and 500. Even between 200 and 300 mm. I have a 300 mm and my husband has a 200mm. Hates with 200 birds when we're rolling. He can not get as close as you can. So now he is the saving of 300 mm. Given the 50-500mm lens is a lofty goal big … that f4 is pretty good. If I had money, I buy the 50-500mm. I would rather have more zoom. But again, I shoot wildlife and landscapes.
Nikon D90 HD Video : Nikkor 80-200 f2.8