----- Original Message ----- From: "John Celio"
Subject: Re: 50mm/f1.4 Takumar lens: question about yellowing
Do they all develop a yellow cast over time ?
This is something I've been wondering for a while now, too. A few of the older Takumar lenses at the shop I work at have yellow casts to them. I initially figured it was just some sort of weird coating (or lack of a coating), but now I'm concerned it's something else. Anyone have any definitive info on yellowing in old lenses?
Pentax used slightly radioactive glass in some of their lenses. These are the ones that are prone to yellowing.
The cure is to shine a UV light source (blacklight) through them for a month or so.
William Robb
