So the next lens I'd really like is a 50mm. I've been looking and saw a Minolta AF 50mm f/1.7 for £75. Is that a good price for it? I already have a Tamron 55-200, a Sigma 28-70 (plus an 18-70 kit lens which I don't like much). I find most of my portraits on the Sigma are taken around the 50mm length and 100mm on the Tamron. Eventually I'd like something really wide for architectural and landscape photos, but a cheap 50 will be more use to me at the moment.