Almost any of the 150-600 mm lenses work great.
This a crop.
This shows how far away they were. One of the dots in the water are these otters.
Again the purpose of a super telephoto for wildlife is to make small animals look larger in the frame. Or put another way fill the frame with the subject. To this getting closer is key. Closer is always better than more FL. As you distance increases the ability of the lens to resolve the subject goes down as seen from the critters in the cliff/ocean photo above.
I was about 35' to 40' from this magnificent hawk. He/she was getting impatient from my intense interest in taking the photo.
Telephoto lenses let you keep a safe distance form subjects that can express their will, sometimes forcefully, on you.
A crop of another shot of the same hawk.
EOS 1D Mk IV, Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens@600mm, f6.3, 1/2000, ISO 800
The 400 f5.6 that Ernie mentioned is a very good lens that I have owned for years. In addition to producing sharp images, it also focuses very quickly which is critical for wildlife.
There are times that the 1.4X extenders are useful but with the increasing pixel count of DSLRs and sensors that offer excellent images with a moderate number of pixels (like the 20 MP sensor used in the 1DX III), cropping versus using a 1.4X is something to consider.
I went to Iowa earlier this week to photograph eagles and most shots were with a 1DX III and EF 800 f5.6 and I used a Canon 1.4X converter part of the time but even with an expensive prime and 1 series camera the focus acquisition slows a bit and that effect is worse with less capable lenses and bodies. When the eagles were sitting still, I used the 1.4X some but in general I found I was happier with the bare lens. And as Ernie noted, the closer you can get the better but since the river ice was thin (which is why the eagles were there) I wasn't going swimming in freezing water with my cameras 🙂
This series was shot with the 1DX III and bare EF 800. Once the eagle was on the ice, I could have added the 1.4X but if I had done that I likely would have missed the next good eagle action. These images were all using around 25% of the 1DX III's sensor so pretty heavily cropped.
Rodger
And it is also easy to have too much focal length at times for wildlife. This is where zoom versus prime comes into play and sometimes it would be better to give up some focus speed and sharpness for the versatility of a zoom. With fast moving wildlife, even with a zoom you don't want to try to nearly fill the frame because the movement is too unpredictable. Shooting football I can do pretty well filling much of the sensor area with the desired subject but unlike football I have almost no ability to predict what wildlife is going to do.
This next series is an example of too much focal length. This eagle was doing some interesting maneuvering and I was tracking him nicely with the EF 800 when he suddenly went to full afterburner on a vector in my direction. If I hadn't been freezing in 8F weather with a heavy wind I might have been able to switch to my second body with the EF 400 f2.8 in time but close only counts in horseshoes and hand grenades so I missed a golden opportunity. The first shot I didn't anticipate his dive speed rate of change and the very shallow depth of field got me so he is not quite in critical focus and not in frame. The next two are a little better but the eagle was moving too fast to frame perfectly. If you do frame such a shot perfectly, it will be an incredible shot but the odds are very much against you. So if you go with a zoom, don't attempt to over zoom when using it.
Rodger
