Hi Brendon. Thanks for comment. I really appreciate that. All what you write, I know. 17-40mm is my "basic" lens, I have also EF 50mm 1:1,8, but I didn't use it here, because I need quickly change angles and more wides angles then 50mm (80mm - because crop factor 1,6) in this series. Life is full of compromises.
Pretty girl. You have nice equipment, even though the 17-40mm f/4 is an excellent lens, I would not recommend it as an individual portrait lens. It can be as used a family group portrait lens. I would recommend a portrait lens in the telephoto range of 80mm thru 105mm. With the 1.6x factor or crop sensor on the Canon 50D, you should be able to used a 50mm thru 90mm. These lenses can either be prime or zoom. A short telephoto or portrait lens will control some distortion that will get from wide angle lens. Look at the girl hands. They look kind of large for her body. Also, portrait lenses have better control of depth in field. Try shooting with a wider aperture and less ISO speed. You don't want your background to be in focus. You did a great job capturing of lighting of the skin tones and the seperation of the whites color.