Wildlife: Canon EF 100-400 VS EF 70-200 f/2.8 L IS MKII + 2x Extender MKIII

[Chromarok]

Hello

I am about to acquire some L lenses for my 7D and now I'm a bit confused on what to go for, due to the various advantages and disadvantages of the lenses I am considering.

I mainly shoot wildlife and nature, and I will likely be doing a reasonable amount of shooting in not-so-favorable weather, so I may have the need to expose my lenses to the elements from time to time (I do have a storm jacket, but it is quite cumbersome for handheld use). I also really do need the 400mm. I have a 300mm Tamron with me at the moment, and even on an APS-C camera, I find that sometimes it is not enough.

The option that appeals to me the most is buying the 70-200 f/2.8L IS MKII and a 2x Extender MKIII. It is a weather sealed setup, offers the 400mm I need, and I get an f/2.8 tele whenever I need. However I am worried about:

• Focusing speed & accuracy
• Sharpness compared to the 100-400mm f/4.5-5.6L @ 400mm

If someone could provide some 100% crops of both lenses It'd be great, if not I'd love to hear your opinions just the same.

The other setups I have as an alternative are:

EF 70-300 f/4-5.6L and EF 100-400 f/4.5-5.6L (one being weather sealed)
EF 70-300 f/4-5.6L and EF 400mm f/5.6L (both sealed, but limited to the prime if 400mm are needed)


Thoughts?