Hi Bruce & Boris Sirs, New Year Greetings. Pentax does not use optical plastic elements in their K- mount lenses including the 18-55 kit lens or the cheaper primes. Yes they do use plastic in the Aspheric lens elements. This plastic is deposited over the glass lens in ridges. Hence aspherical elements do not have a perfectly smooth finish over the lens curvature as in pure glass lenses.
But due to manufacturing or material defects, some aspheric lenses have shown separation and damage between the plastic and glass interface in the form of fogging - like if you lightly sandpaper a clear glass sheet. Some very expensive lenses do not use plastic deposits on aspheric lenses at all. Instead each ridge is cut and polished in the glass itself. This explains why such lenses are very costly and why they are so sharp too. Regards. Bipin. -- 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.
