I currently have a Rebel XT, Speedlite 580exII, Sigma 28-70 f/2.8, and a Canon 50mm f/1.8.


I love my XT, but my Sigma lens is driving me crazy. I'm not sure if I've gotten a sharp shot out of it in the 3 years I've owned it, and now that I'm getting more serious (and have a bit more spending money), I'd love to upgrade it.


I shoot mostly landscapes and portraits, thinking about trying to do some senior photo shoots for some extra cash this summer.


I tend to shoot most of my shots of people at the wider end. Some of my favorite shots are full or half body portrats at 40mm (on a 1.6x) or wider. A quick glance through my adobe bridge showed that I rarely hit the 70mm mark on my Sigma.


With that said, the other day I did use my wife's 70-200mm kit Nikon lens for some portraits that turned out nicely.


I love the framing that wider lens give, but I love the bokeh that longs lens give. Is there any way to combine the best of both worlds?


Edit: I'm looking at both the 17-55 EF-S and the 15-85 EF-S. Any opinions on the difference? The extra length and lower price is appetizing on the 15-88, but the 2.8 also looks nice for the 17-55.