I have a Canon 30D and am using a Sigma 28-105 IF 3.8-5.6 lens. I am getting more and more portrait work and need to get a higher quality and faster lens for my exclusive natural light work, somtimes indoors. I do a lot of kids and mostly close-ups, so the background blur has been ok so far and I usually hand hold. Also, I don't understand some of the techinical aspects of my 1.6x sensor and how it applies to final images. If you shoot at 85mm with my current zoom lens- does it mean it appears that it was shot at 135mm? Not sure how that works and I want to understand before I spend a lot of money on the wrong lens. I am on the fence about a fixed length or zoom, but know I need 2.8 or faster for the best quality. I can go the Canon L series if it's a must- but I'd like other suggestions in the Canon line. I was looking at the 70-200 2.8L USM, but it may be too long with the 1.6x factor?Thanks!