I'm considering buying a long zoom and have looked at both the 50-500 and 150-500 Sigma's. I've noticed that the old 'Bigma' is classed as an EX lens, which I understand is short for excellent? The newer 150-500mm is missing this lettering, however. Now the obvious thing would be, to pop into Jessop's or Jacob's - or so you would have thought? I'd have been better off asking in B&Q! Do any of you guys have any idea if the newer lens is of a lesser quality? Also, I'm torn between one of these Sigma lenses and Nikon's own 70-200 f2.8 with a converter. Basically, I want some one to make the decision for me
