And of course this is the correct answer....
"I would recommend the 1.4X if you can only afford one.
I'm sure you probably know this, but the Canon extenders only work woth with certain Canon lenses ..."
In general extenders are a poor idea. You give a lot to get little. There are a few "L" lenses that tolerate an extender fairly well. Most lenses don't. The Canon EF 70-200mm f/2.8L IS II USM Lens and the Canon Extender EF 1.4X II work well together. I have this combo so I can recommend it. It also works well with the Canon EF 300mm f/4L IS USM Lens. Again a personal tested combo, I can recommend it. As a general rule they don't and you should avoid lenses that are slower than f4 with an extender. And f2.8 is even better. And again, IMHO, avoid the 2x altogether.
Then you get into the really super tele like the Canon EF 500mm f/4L IS II USM Lens. Although the 1.4x works OK with it, it brings some more difficult limits to over come. At a 700mm FL, it can be quite a challenge to use. I do not own that combo but I have rented it.
EB
EOS 1D, EOS 1D MK IIn, EOS 1D MK III, EOS 1Ds MK III, EOS 1D MK IV and EOS 1DX and many lenses.
