Can someone offer me a realistic reason why the 14-140mm f/4.0-5.8 is only $20 cheaper than the 14-140mm f/3.5-5.6 lens? I understand it is lighter and slightly smaller, but if it isn't any better, why is it being introduced at all? If the latter (f/3.5) was significantly better optically (which no one to my knowledge has demonstrated), I could understand a more significant price difference. As it is, I don't understand why (1) they are both on the market, and (2) only $20 different in price. Please enlighten me.