My camera is 50D, my main lens has always been the 17-85 I got 5 years ago. I've come along way in skill to know that I've definitely outgrown this lens. The wide angle is important to me, but this lens is just too soft a focus and I mainly due editorial fashion photography but use it as my walk-around lens since it's got a lot of focal zoom. (Though at either end, images fall very flat! Especially around 50 + the photos look so point and shoot). The amount of post-process sharpening I do ruins the skin even though I shoot 100 ISO, so I spend a lot of ps time trying to perfect skin and sharpen and still I feel my images look flat. I get better results with my thrift found sigma 28-70! I've researched the lenses available at this focal length and wanted to hear from someone who has used the 17-85 before, I want to know if there is a noticeable improvement between the 17-85 and any of these, I kind of want a wow factor: Choice one: Canon 15 - 85. First thought is that it is 2 cm wider which excites me and it keeps. It's a little bit faster. I love the photos on the flickr group. The large amount of zoom appeals to being a walk-around as well. Of course I am wondering if this isjust the same as the 17-85 plus 2 CM? How will it perform zoomed, how are lines: worse or better? Choice 2: 17-50 sigma/tamron 2.8 Among my comparison charts and looking at flickr pools, both the tamron and sigma's photos look as great at canon's 17-55, I might be fooling myself here, but it doesn't look like there is a 500$ difference at all. I like the constant aperture, this is a lot faster than my canon. I lose a bit of mm, but for my photoshoots I really don't go above 50mm using the wide angle anyway. Argh, the many options for this range makes me slightly crazy! Which lens is the best contender?