I have Canon 350d with 400l prime, 70-300mm tamron and a very poor 28-90mm. I am covering some weddings this year. I am considering Tamron 17-50 f2.8, Canon 17-85 f4 IS USM, I would welcome thoughts especially if you have owned or used these, I am also open to your words of wisdom and if there are better lenses for £300/$550 then please enlighten me
1. You won't be needing the 400mm, unless you plan on shooting the couple from down the block.
2. Get rid of that "very poor" 28-90mm and get yourself a F/2.8 normal zoom, preferrably the Tamron 17-50 if you can't wing for the Canon 17-55 IS
3. You WILL need a flash, Canon 430EX if you can afford it, 420EX if you can't (this one doesn't have manual control but you can use the 350D to control for FEC)
4. You should spend $80 on the 50mm 1.8 I/II for low-light exposures and portraits.
Are you doing this wedding professionally? I am not dissing your equipment but there are some basic equipment that you don't seem to possess. I was a guest at my friend's wedding 2 years ago and I had much better equipment than the hired photographer. He was shooting with a 20D + 17-85 IS with a Qflash. When the bride compared our pictures, she and her husband overwhelmingly chose my pictures to be better than his. Don't take on a wedding that you can't deliver, it'll make your life and, most importantly, the couple's lives miserable.
I'd sell the existing equipment and pick up a pair of used 30D's with a 17-55IS, an 85mm 1.8, and 50mm 1.4. You'll also need at least two external flash units, extra batteries, and plenty of memory. As you make money with weddings, you can expand that kit to include at least one more DSLR body, another flash, a 70-200 2.8IS, and a 100mm macro lens. And you probably ought to consder a Tamron 28-75 as a backup lens, in case one of yours fails.
