http://www.nikonchat.com/80-400mm-nikkor-lens-2/

for all you Equestrian Event Photographers… lens question?
I do mainly Equestrian Show Jumping photography and I am looking for a new lens. I just got a brand new Nikon D3s. I am trying to decide between either the Sigma 120-400 F4.5-5.6 DG APO OS HSM or the Nikkor AF VR 80-400mm f/4.5-5.6D ED. Also, will these lenses be ok with a tele-converter? Because when I shoot in stadiums I need a little extra zoom sometimes….. Right now I just have been using a cheap 70-300 Quantaray lens…not very happy with it.
Thanks!
I am also open to other options
No. Those are all way way way way way way way too slow. And a teleconverter will only make it worse. Push that fancy D3s to 103,000 ISO or trade that sucker in for a fast lens. I’m sorry to be a jerk about it and I honestly want you to enjoy this thing that all of us here love so much but you are making foolish decisions about how to accomplish what you want to do.
A normal camera with a telephoto prime lens is how you will get the photos you want. A 300 2.8 on a aps-c body gives you the speed and reach. Or a 85 1.7 on a 4/3 body also gives you sped and reach. You can also pump money into a 50-500 but you are looking at a 5.6 anyhow. or 800 4.5, same problem.
Again I want you to have fun and enjoy the hobby but you can’t keep thinking a name or a number will be a savior like Christ. Get a lens that is appropriate to the situation you want to do. Then a body with the money you have left over. Your past choices in equipment have been incorrect and the consequence has shown in your results.
Nikon 80-400mm f4.5-5.6D