neuroanatomist said:dgatwood said:On the flip side, with the -3 EV center point, you might get more keepers in low light with the 6D than anything else Canon sells (including the 1DX). I've found its low-light focusing to be just plain spectacular.
How do you define 'low light'? For example, the difference between shooting at -2 EV and-3 EV could mean 1/15 s, f/2.8, ISO 51200 vs. 102400. Neither is very usable from an IQ standpoint. What most people call 'low light' is generally substantially brighter than either spec.
I agree that "works well in low light" or similar phrases have a rather imprecise meaning. I thought that Canon's spec on the center point is rather more precise than that, center AF point sensitivity down to EV -3 (at 73ºF/23ºC, ISO 100), which for example would be an 8-min exposure at f/8 or 1-min at f/2.8. Perhaps familiarity with night photography might help envisioning what level of available light would call for such an exposure (considerations on what constitute an adequate exposure aside).
As a side note, I can report using live view AF in the 6D for night landscape shots of 16-min at f/8, ISO 100 (EV -4). AF is rather slow and requires judicious use when choosing your subject. I wouldn't use the viewfinder in those scenarios, as I've found it too dim and small. I haven't heard/read anything pointing out that other cameras wouldn't do as well as the 6D is these circumstances. But I've personally witnessed other photographers resorting to MF quicker than me in these situations (technique and preference may play a role as well).
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