Archived posting to the Leica Users Group, 2007/11/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]On Nov 7, 2007, at 3:10 PM, Leonard Taupier wrote: > 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. I'd use a black light 24h... as glass blocks UVB and some UVA....which is the active wavelength to rejuvenate the lens...? Steve > > > 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