pentax used "modern" plastic on some filter rings of their f series lenses. those rings often crack and break off with age. Metal is better.
----------------- J.C.O'Connell [email protected] ----------------- -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of James King Sent: Wednesday, May 23, 2012 8:48 PM To: [email protected] Subject: Re: New DA50/1.8 Plastic Mount P. J. Alling wrote on Wed, 23 May 2012 09:20:38 -0700 > Lenses are a long term investment, at least they used to be, plastic on a bearing surface implies the opposite. No matter what plasticizers are lost over time and the material becomes brittle and subject to cracking. Eventually something important will break. Heat will exacerbate this process. If the lens was cheap enough to be disposablethat would be fine but it's not really. It ain't neccesarily so! I'm confident that the Pentax plastic lens mount is made of a modern engineering plastic; these are heat-resistant, often self-lubricating, and do not contain volatile/migratory plasticizers. Unless subjected to severe mechanical stress it's likely that they will outlive the user. Regards, Jim -- 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. -- 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.
