Asher Kelman said:
I don't think it is fair, Aaron to a Sigma Zoom to teast it against the 300 2.8L IS. The latter is one of the fines lenses built.
The Zoom should be compared to other practical lenses such as the 100-400 Canon push pull zoom.
The prices and intended functions are more closely related.
No argument there. I already know the limitations of my Sigma. It's very slow to focus and quite soft wide open, particularly at the long end. And comparing an f/2.8 lens against an f/5.6 lens as far as autofocus performance is concerned is also a fools errand. Consider that a poorly executed attempt at humor.
A more valid test would be against a Canon consumer zoom. They just happen to have a newly updated 70-300/4-5.6. It has IS, but that's not relevant. Even having USM (I don't recall if that lens does) shouldn't matter, as I'm concerned not with focus speed but focus accuracy. Perhaps there's an issue with Sigma's reverse-engineering. Unfortunately I don't know anyone who has such a lens for me to check.
The fact that I have similar issues with my Sigma 28-70/2.8 suggests a Sigma problem or a problem with my camera. I have to separate the two to get to the bottom of this, hence my question about other's experiences with Sigma lenses on Canon bodies.
What I could test with a 300/2.8L is if there's an issue with my camera. The most likely cause that comes to mind is a misalignment between the AF target in the viewfinder and the actual sensor. That would explain a lot, as most of the out of focus images were actually focused on a more distant subject (a few were not, probably issues with focus speed). I'll have to see if I can develop a test for that. Shouldn't be too difficult.
That being said, just because Gary uses the "Bigma", is, IMHO, already a pretty good endorsement. If you check his galleries he is a very experienced, artistic and choosy photographer and I doubt he would bother to carry around a big heavy object that didn't work as expected.
Agreed. That lens is still not exactly cheap, so I'm sure Gary wouldn't put up with the problems I'm having. It's also 1/3 stop slower at the long end, which should make focus an even bigger problem.
Part of the problems people have is technique in using the lens. I have heard people "testing a number of these just to get a good copy". So certainy test the lens immediately on buying it!
I don't recall these focus issues with the film body for which this lens was originally purchased, but that may also be due to the fact that I haven't shot a frame of film in several years. Given that my 70-300 lens is over ten years old I was pleased that Sigma re-chipped it for free. I've been pleased with the lens given its price point. I just need to figure out the source of my problems before I go insane. Shooting sports with the world's slowest focusing lens isn't easy, but when it regularly picks the wrong focus point it's downright frustrating. It would be even more irritating to buy a $1700 70-200/2.8L IS and have the same problem.
This has really turned into a lens discussion and this is the wrong forum for that topic, so let me close with this: nice shots. After a few hours over the weekend trying my hand I am reminded how much practice goes into doing sports photography (or any other type, for that matter) well.