The Tamron Adaptall-II SP 35-105/2.8 ASL is a great lens that isn't too expensive these days, though it was originally one of their top line lenses, with a wide constant aperture and aspherical elements. It's very sharp, but like all tele-wide zooms, shows a little barrel/pincushion distortion at the extremes of the range. So it's not ideal for architecture, but it's perfect for photographing people at events, where you need to move quickly from portrait to group-shot and can't always stand in the ideal position without other people getting into the frame. Constant aperture will also give more consistent exposures with non-TTL auto flash or an external light meter.