I shoot with a Nikon D80. I'm looking at upgrading my zoom from a Nikon 80-400 to a Sigma 150-500 for a number of reasons.
The AF on the lens can be very slow, not very good, for example, for shooting at the local AFB or for the jet acts at airshows.
2) Softness/General Image Quality
Can be very soft at times, especially with lower apertures. Colors aren't always that great.
3) Focal Length
I'm looking for just a little bit more reach.
Would the Sigma fix any of these problems? How is the build quality and overall image quality through the zoom spectrum? Is there another lens that I should be looking at for these results (at a similar price and reach)?