Bingo.. I was wondering when someone was going to mention this. When shooting in good light I sometimes use a 1.4.
Most of my shooting is in dismal light. Making T.C. work miserable for me.
I was in a hide shooting pittas about two months ago. With my F/2.8, 300mm using the 2.8 focus points of the Mark IV. I was running circles around the other photographers. There was no comparison. I ended up with the best shots by far in a few minutes. Where most hard core birders had been there for days.
Moving from F/2.8 to F/4.0. Makes a noticeable difference in AF performance. Simple things like this will get the shots others will not. I have run circles around guys shooting 500 + 600 mm F/4.0 lenses in very poor light. Many ask me why aren't you using your 500? I just smile and start shooting the eyes out of the birds. While they are having to move back and suffer the handicapped AF performance of F/4.0.
It is the main reason I own a 300 2.8 lens. Over here the guys that run down the 300 2.8 saying it is to short. Loose big time in low light close quarter shooting which is common in the jungle.
I am looking forward to the next generation of cameras. I skipped the IDx. But would love to try one just to play with the AF.
Great hobby. Just a lot of fun...www.flickr.com/photos/avianphotoswww.birdsthatfart.com