The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))
A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.
My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.
Question: So according to this f2.8 is more important for available light and movement shots, but if that was case with the 5d2, I'm confused why still seems to be still valid with the 6d even though it's about 1 stop better ... either f2.8 was borderline in the past, or f2.8 - 1stop = f4 would be sufficient now - or am I missing something here?
Disclaimer: Please forgive slight traces of irony, this ia a real question because I don't entirely understand the issue, it's great people get whatever gear they like for any purpose they want.
The minimum for capturing action on what I've found to be typical indoor light is:
1Ds Mark III/5D Mark II + f/2.8
5D3/6D/1DX + F/4.0
The thing is that f/2.8 on a 5D Mark 3 gives you more flexibility, you aren't at the limit, so you're more comfortable.
The zoom range let's you frame shots better, and bokeh at f/2.8 is right at the boarderline between overpowering and pleasant.
So in the end f/2.8 on a newer full frame body is the optimum setup for getting a wide range of shots. Now shooting a f/2.8 lens at f/4.0 will often deliver sharper images than going with an f/4.0 lens to begin with so there is a disadvantage to going f/4.0 to begin with, and you have less flexibility (as you don't have the option of f/2.
Going to an a prime that's faster than f/2.8 limits you because there is no zoom, you want SOME zoom if however small it is just so you can get framing right.
F/2.8 tends to be a good "all around" range. You have zoom, bokeh, and a comfortable amount of motion stopping without flash.
Personally I have a collection of the following lenses:
24-70mm f/2.8 II
24-105mm f/4.0 IS (for landscapes, still life and other times where IS helps more than f/2.8 because there is no motion to stop and for when I don't want the onion bokeh or focus shift of the 2.8 II)
70-200mm f/2.8 II
Sigma 35mm 1.4
Canon 50mm 1.4
Sigma 85mm 1.4
24mm TS-E + 1.4x TC & 2x TC (35mm TS-E & 50mm TS-E)
Ideally I'm looking to pick up a Canon 200mm 2.0 too