HI James,
I was considering the 50-500 Sigma, but again I don't like having the F Stop
vary etc. I think the 100-300 Sigma F4 would be a better choice. I'm going to rent that one next to give it a try.

Any of the lenses that now have the image stabilization seem to have that
extra edge for hand held situations that seem to catch you by surprise.

I feel more comfortable having a lens at the ready and mounted on the camera to catch those moments that sneak up on you.
That way you can capture a few quick shots and hope that they come out. Then it's time to get out the tripod , turn off the stabilization and get to work.

I always shoot wildlife with aperture priority, wide open at first to see what
the background will look like. (bokeh) etc. That way I'm seeing exactly what the camera will capture.

I'm rambling now, but I do have a point that I was trying to get to.

This image was a challenge and it all happened very fast.

I was photographing the young buck on the right with my Nikon 50-300mm EDIF F4.5, with my Benbo tripod and a Slik Pistol grip.
wide open and at 300mm. Then, another buck approached from my left side, but much closer to me. I was able to zoom back to 50mm, change my F stop to about F8 and capture both bucks as they were checking each other out. This lens is not autofocus, doesn't have any stabilization, but it is one of nikon's best lenses of it's time.

Just some of my thoughts to share.


Dale