Archived posting to the Leica Users Group, 2007/11/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Len, maybe the best methods might be to walk around outside in the sunshine, better shoot wide open. Don't forget the film! Cheers Hoppy -----Original Message----- From: lug-bounces+hoppyman=bigpond.net.au@leica-users.org [mailto:lug-bounces+hoppyman=bigpond.net.au@leica-users.org] On Behalf Of Leonard Taupier Sent: Thursday, 8 November 2007 08:10 To: Leica Users Group Subject: [Leica] OT: Fixing radioactive lenses I have an old Pentax 50/1.4 Super Takumar that has, over time, yellowed due to one of the elements containing Thorium, a mildly radioactive element. The addition of thorium makes a very high refractive index glass, and a very good lens. This lens is probably one of the most famous lenses with this element but I'm sure there were more. The fix for removing the yellow cast to the lens is to expose it to a UV source like sunlight or a UV light for a week or more. I have been putting the lens in a window during the day and exposed to a black light at night. My question is concerning the glass used in my windows. They are made of high E glass and have an air space between the double panes. I know high E glass is supposed to suppress Infra Red but I see no info on if it passes Ultra Violet which is at the opposite end of the light spectrum. Does anybody know? Thanks, Len _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information