Canon 100-400 USM L w/ 2x II Extender

[hounsell]

:confused: Has anyone experimented with using a Canon 100-400 USM L lens w/ the Canon 2x II Extender? I had a family member pick me up one, and found out in aftermath that I can not autofocus (found out after I landed in Alaska no less). Long story short, big bummer. I have tried using it for really close range animals (in manual) with decent results, but nothing longrange, as I can never focus perfectly resulting in blurry pictures. Looking for last minute advice before I throw it on ebay and take a hit on the price.

[joeseph]

Hi Hounsell, welcome to the band.
lots of folks have tried - few get autofocus.
have a read of the sticky thread for more info:
http://photography-on-the.net/forum/showthread.php?t=41922

[Jon]

Canon's specs are that their entry-level and Prosumer DSLRs require a maximum aperture of f/5.6 to Af. The Pro (1Dx) series will AF with a max. aperture of f/8. When you put any teleconverter on a 100-400, it's out of AF limits for anything but the 1D series. The 2x TC on it won't AF on any Canon.

Whether an animal's close up or distant shouldn't affect how well you can focus on it, if there's reasonably good contrast on the subject. If there's a lot of haze, it may kill the contrast so you have difficulty focussing manually, but that's not strictly distance-related.