On Mon, Jan 6, 2014 at 10:11 AM, Bruce Walker <[email protected]> wrote:
> That's a good question, Boris. Not being a gearhead I don't closely > study the fine details of lens construction, but I assumed that only > glass was hard and stable enough to be ground or milled into shape > with the required tolerances. > > Does anyone know if plastic, or anything besides glass and coatings is > used in the optical path of any K mount lenses? My understanding is that plastic elements are normally molded, not ground. For aspherical elements, it's cheap to mold plastic, since you only have to machine the aspheric shape in the mold, rather than each element you produce. I think this is common for things like cell phone camera optics. I don't know for sure whether plastic elements are used in Pentax lenses or not. Someone on PentaxForums states (without proof) that the 18-55 has plastic elements, and that wouldn't surprise me, given that it's cheap and has "AL" (aspherical) in its name. Matt -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
