From browsing the pictures at Fred Miranda I knew I wanted to get a fast prime lens for portrait and family shots. I liked the look of the photos shot wide open with a variety of the fast lenses. I also knew I needed auto focus. Thirdly, price was a big factor. This lens got great reviews, is built very solidly, and I liked the really smooth bokeh look. If I had unlimited funds, I would have bought the Canon f/1.2 because I think it has better contrast and colors. But I don't, so this will do for now.