Joe, I merely meant that a good lens is one which does what you want, not one which has all sorts of capabilities you're not utilising. If you want the nocturnal light, a certain bokeh, a certain plane of focus, well it matters not if it's a £100 manual lens or a £2000 silent-something-technology 5kg tele-zoom. That's all. I was going to suggest that a lens needed to adjust it's elements to accurately focus but I realised that focus was about what you were trying to do with it. Focus doe snot always behave in the way it should if one is to go by the thousands of comments on lenses and samples out there on the web.