Like the famous Canon white focal length is 70-200 mm less than 3 times the look, and the maximum aperture constant at F2.8, with no dispersion (purple side) of the fluorite lens! The Saying that if the landlord do not understand these most basic things, my advice is not easy to SLR!
Such as 18-135 zoom ratio of 7.5 times, 18-200 zoom ratio of 11.1, so theoretically 18-200 of the picture quality is certainly not as good as 18-135, and in fact the same 18-200 imaging comparison 18-135 Said to be much soft, scattered also large, you see the majority of those on the pitch is 300,400 or 600 mm fixed focus lens, these huge lens is not zoom is 1 times, picture quality is quite good!
Not all, mainly to see the largest aperture and lens composition. For the lens, the greater the zoom ratio, the worse the optical quality!
