Postby Notorious Scullman » December 8th, 2009, 1:16 am
Maserati, from the reviews I read some months ago, the Sigma is just as good all-round as the Canon f/2.8.
f/4 lenses are all well and good for bright sunlit sports, but once you have an overcast day, or start heading into dusk, you'll appreciate the benefits of the larger aperture of the Sigma.
I own a Canon 70-200 f/4L and it is an incredible lens, but having used a few Canon 70-200 f2.8L's (and pretty much any high-end f/2.8 lens for that matter), it's not a difficult decision to make to go for the larger aperture.
However, and it's a big HOWEVER! Canon L lenses typically do not depreciate, once well-maintained.
Sharpness at f/5.6-f/11 IMO is irrelevant, as you intend to shoot subjects in motion, where shutter speed and light sensitivity would be your priorities.
Something to bear in mind is that your flash (whether pop-up or hotshoe) has a much further effective range at f/2.8 than at f/4, and flash freezes motion.