on the 2.8 reason, there are multiple reasons:
first- on your 50 f/1.8 you really need to stop that down to 2.8 to get a decent focus on it. shooting at 1.8 leaves the image flat and due to poor qc on those lenses you usually get a lot of crap focus on the edges.
Crap focus? It's f/1.8. Nearly everything is going to be out of focus. That's the point.
If you have a specific problem with a specific piece, you return it or junk it. It's a $100 lens and when it's right (and honestly, I've seen no QC issues any more than any other lens, unless Canon is significantly worse than Nikon here), it's sharper than any zoom is ever going to be, stopped down or no. Even if you DID have to stop it down to f/2.8, well, you're still at the starting point for that 10x plus price zoom.
on the 24-70 f/2.8 it is one of the few zooms that is really sharp at 2.8 , but it's an L lens and you get what you pay for.
I'm sure it's the same as the AF-S Nikons. The real ones, not the one I have alluded to above which is "AF-S" but isn't really. The one I have is an incredibly sharp lens with a bit of distortion at the ends.
I'm not denying your lens is great, but in that focal range, you're not talking about differences that are not actually going to matter. That range is not telephoto enough for portraiture (you want at least an 85 f/1.8 for half the price or 85 f/1.4 for about the same, if not longer), not telephoto enough for sports, and you don't need super-low f-stops at the wide end anyway (amount of light needed at 24 f/3.5 is roughly equal to that of 50 f/1.8; 24 f/2.8 = 50 f/1.4)
Sometimes you don't have the option of foot focusing a lens- think about shooting a concert with a photo pass where you are stuck in one location to shoot- foot zooming doesn't work there.
I have done concert photography before, actually, though not on a photo-pass basis. Generally pass holders are way up front, so I'd want two bodies - one with a 17-35 (stage/area/crowd shots) and one with an 80 - 200 (head/bust shots), the range in between is simply not useful. 35 - 80 range is the "birthday party" lens, and you're going to be using flash, 400 speed film, and want lots of DOF so no way is f/2.8 wanted or necessary in such a situation.
Also, the 24-85 is not even nearly as clean a lens as L glass.
"Clean"? Are you talking about sharpness or distortion? Because from all accounts, the 24-85 f/3.5 - 4.5 AF-S is as sharp as it gets for a zoom (I'm sure the Canon equivalent is equal), though again there is significant distortion, but that is what Photoshop is for. For any potentially "award winning" photography you are shooting slide film, and all slide film is now printed digitally anyway, so you will have ample opportunity to run it through PS first through a correction process you can pre-set for every lens you own and then apply in less than a minute per pic. All for a quarter of the price and less than half the weight! Besides, if quality is your drive, shoot medium format
But don't take my word for it; see what an actual professional thinks of such lenses:
http://www.kenrockwell.com/nikon/2870afs.htm
Topic: Giving in to temptation: Canon EF 24-70mm f/2.8L USM (Read 9439 times)