Upload & Sell: Off
I've just about had it with the 5d3 to the point of selling it. Yes I am using firmware 1.2.3 version.
My 5d3 AI servo is terrible in low light (think ISO2000-3200 1/125 f/1.8 or dimmer). Center point or anything else. Terrible, it misses focus so many times with dancing subjects, laughing subjects, walking subjects, etc., it's not even funny. If I expand the AF points to lock on different targets, it ends up missing more. All of my 5d2s do a better job at this with the center point than my 5d3 with any point (including center).
5d3 obviously does just fine in good light, and in good light the outer points are an advantage. Yes I am using firmware 1.2.3 version.
D800's tracking system is, from my limited experience, smarter than 5d3 tracking.
My 5d3 One-Shot is terribly SLOW in low light with AF assist. Yes I am using firmware 1.2.3 version. I performed tests with a non-moving camera in my own house side by side with the 5d2, and the 5d3 beat the 5d2 more often than not for focus locking speed in One-Shot. However, in real world, the 5d3 takes twice as long (or longer) to lock in One-Shot when dealing with low light.
I'm not a still, nonmoving object like a tripod, and neither is the subject a still, nonmoving object. In real-world receptions, my 5d2s nail focus nearly instantly, my 5d3 takes seemingly forever and sometimes misses the shot anyway. It's like the difference between "ok it's dark, ZIP, lock dead on (5d2)" and "ok it's dark, start focusing, wait wait hang on, did I get it right? better go back a little, let me check again, okay just a little longer, I think I got it, okay lock confirmed probably (5d3)."
Does ANYBODY else besides me have these issues with the 5d3's AF compared to the 5d2? To-date I've only seen a few very limited comments talking about this particular focusing behavior of the 5d3 besides my own...none of them on this forum...