I am in the market for a 75mm f4.5 Pentax 67 lens and there are the two versions. The old one that is heavy, all metal and built like a tank. And there is the new version that is much lighter and made from some carbon material I suppose. Just handling the two types I would think the older one was better and would last forever, but is that true? The older style is much heavier. Does anyone have experience with both and is the newer lens superior in any way other than weight? thanks Dennis PS anyone have a 75 they want to sell?