This is indeed one of the most annoying problems with Canon Powershot SX50 HS.
If it's auto focus fails, the user of the video mode is pretty much f*cked.
Zooming in and out may help the auto-focus to get the focus better, but when trying to zoom back in it might still f*ck up.
Really annoying, and really bad about this camera. I guess older cameras has a cicular control/numb to change focus but with this camera it's gone... pretty shitty.
Anyway, the dial could be used to change focus... I think that could be a nice option or the buttons as long as it doesn't suddenly "over-focus"... it has to do it gradually and such oh well... or maybe exponential... hmm...
centimeters, meters, etc... hmmm... or maybe just multiple buttons that's probably easiest/best:
centimeter adjustment button, meter adjustment button. so user can adjust focus quickly/largely or slowly/finely.