*sigh* wrote in post #13634709
Ah yeah...
Could you go with a 400 5.6 as a cheaper option? It's a little redundant FL/F stop wise to your 100-400 but it should be quite a bit sharper.
The 400 5.6 blows the 100-400 away. I can't say enough nice things about the 400 5.6. It's priced right, the AF is superb, it's incredibly light, and the contrast/sharpness is almost sublime. I can't comment on how it compares to the 500 f4 IS, but compared to my bunko 500 f/4.5L, the 400L was better from f/5.6-f/6.3. I also think my 100-400L was slightly soft, but compared to the 400 5.6, it's no contest. The 100-400 compares well to the 70-200 II w/2x II TC, and the latter is nowhere near as good as the 400L. I could really see the difference when comparing sample 100-400 moonshots vs the 400 5.6.
I'd already decided to ditch the 500 4.5 and keep the 400 5.6L, and then the cheap 300 2.8 presented itself. Even now I'm reluctant to let the 400 go, because it's ultra-light and portable.
The 100-400L is a great birding and tracking lens... but I'd rather work around the lack of zoom, and only get a fraction of the shots I might normally get, but have them razor-sharp and contrasty. Birders might laugh at the 400 5.6, but that's their problem. Definitely a great performer on my gimbal head--I don't notice the loss of IS at all.
There's little reason to stop down much, if at all. It's about as good as it gets when wide-open.