I have both the 70-200mm f/2.8 IS II, the f/4 IS version, plus both the 1.4X III and 2X III TCs. The f/2.8 is an astounding lens you should consider if the weight is acceptable. It is sharper and focuses faster than the f/4. That said, I don't always need that level of performance for everything I do. The 1.4X TC works well on the 70-200mm f/4 if you need the reach and can give up 1 f stop for the TC and stopping down 1 more f stop to improve sharpness. The 6D is so good with higher ISO levels that you can usually make up for the light loss. The 2X TC, on the other hand, is a compromise with the 70-200mm f/2.8 from the aspect of auto focus. If you are shooting relatively stationary or slow moving objects, it is one reasonable way to get to 400mm. If you want to shoot birds in flight, forget it. I finally purchased the 400mm f/5.6 for BIF. If a raptor is perched on something, the zoom and the 2X will work, but once it takes off, you are likely to lose focus in the sky and never reacquire focus. The zoom and the 2X get lost, even with the close focus limit set to 2.5 meters. I don't know anything about the other brands, but I think you may regret it from a resale standpoint. The only non-Canon lens I have is a Zeiss 18mm f/3.5 that is wonderful. If the f/2.8 cannot be justified from a cost standpoint, go with the Canon f/4 IS. If I had to shoot a wedding, however, the f/2.8 would be my hands down choice.
Upvote
0