As you mentioned the Canon EF70-200MM f/2.8 L IS USM is awesome, but expensive. Icarry mine to almost every shoot. I have a friend who is getting very nice results with the CanonEF70-200MMf/4, so I think you can have good confidence in it as well.


I own one Tamron and two Sigma lens and none of them produce bad results. Unfortunately mine are not the specific ones you are looking to buy. At high magnification, you may notice some differences versus the Canon "L" series,but they canbe very workable. If you don't venture into 16x20 or 24x36 territory, you may notnoticethe IQ difference.


I really notice the difference in build quality across the manufacturers. The Canon L-seriesbuild is very solid...and I have seen two of them DROPPED good distances and survive. Even when they are damaged, Canon seems to be able to repair them at somewhat resonable cost.