Hi all, I'm looking to buy a new lens and wondering which to go for. I'm an amateur, but have been asked to photograph a friend's wedding next year and have managed to convince myself that I'll need a nice new lens for it..! 
Currently, I have a Canon 400D, with 18-55mm IS
and 70-300 IS
lenses, but fancy something a little fancier for the wide-angle zoom that fills in the missing 55-70mm (both for the wedding and as a general-purpose walkaround lens). The 18-55 is ok, but I find that the images I get with it are very bland compared to those I take with the 70-300.
The lenses I'm looking at are:
Canon EF-S 17-85mm f/4-5.6 IS USM![]()
Tamron 28-75mm f2.8 SP Di![]()
Sigma 17-70mm f2.8-4 DC OS![]()
All seem fairly similar and are about the same price. I'm currently leaning towards the Tamron; the constant f2.8 sounds good... Any advice on which I should go for? Is there another lens I should consider that is around the same price? Or am I falling victim to lens-envy and should just learn to cope with what I already have?
Thanks
Dan

