I m getting a 5dm3 at some point next month (upgrade from my 550d) i currently use a 100-400mm L and will prob get the kit lens with the 5d. Now that upgrade to FF i'll loose some length and was looking into adding an extender to my gear. (cost effective)
I earn money with making videos, but I love to take photos of wildlife, now I've been looking at some extenders, the Canon 1.4 III seemed to be my first choice, but I read it had AF problems on f/8, also I don't really know much about extenders and what others options to consider.
Any suggestions please?
1. The Canon 5D MK III does not autofocus while taking video, so AF with a extender is a moot point. If you want AF while taking Video, check out the T4i. Its not fast AF during video, but it does work.
2. FYI, except for 1 series bodies thru the 1D Mark IV, no bodies AF at f/8. and with Canon extenders, the camera recognizes the f/8 equivalent and will not even try to autofocus.
3. Sometimes a lens will AF using live autofocus with a TC and taped pins (non reporting TC).
Now, before anyone jumps in, I will say that many have reported that the latest Kenko 1.4X extender does AF at f/8 when used with a 1D X, and some have had success using it with the 5D Mark III and certain lenses.
I tried using my 100-400mmL on my 5D MK III with pins taped and it did not work, but the Kenko seems to actually help out.
Your best option is to get or rent a 600mm f/4, but many of us can't afford it much handle the weight.
So, buy a Kenko TC at a place where it can easily be returned if it does not work out.