Archived posting to the Leica Users Group, 2007/11/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Same here and we are referring to the first series with 8 elements ? Joseph -----Original Message----- From: lug-bounces+joelct=singnet.com.sg@leica-users.org [mailto:lug-bounces+joelct=singnet.com.sg@leica-users.org] On Behalf Of Jim Nichols Sent: Friday, November 09, 2007 4:17 AM To: Leica Users Group Subject: Re: [Leica] OT: Fixing radioactive lenses Chris, You sure lost me! I'm just happy that my 50/1.4 Takumar does not display the yellow cast. Jim Nichols Tullahoma, TN USA ----- Original Message ----- From: "Chris Saganich" <chs2018@med.cornell.edu> To: "Leica Users Group" <lug@leica-users.org> Sent: Thursday, November 08, 2007 2:08 PM Subject: Re: [Leica] OT: Fixing radioactive lenses > Well, I'm curious why it even works at all. In a typical application > color is removed from glass by annealing or heating the glass at about 800 > F for a short time and slowly cooling. The time and temperature are the > main issues and a look into glass annealing (ie gemstone and color center > activation) should shed some light. Perhaps a slight elevation of > temperature for 24 hours? > > The UV wavelength for A and B are not high enough per se to cause a > redistribution of electrons in the atomic valence but UV C does have a > high enough wavelength. The only problem is that is how the color is > activated in the first place, by kicking around electrons! In order to > have the process reversed the UV and the glass must have broad energy > states in common to cause enough heat absorption to weaken the existing > bonding allowing new lower energy bonds to form eliminating the number of > electron radicals in the mix. Since UV C is more likely to ionize and > create electron radicals minimizing the UV C would seem like an idea. > Anyway UV C is filtered by the atmosphere so if leaving the lenses in the > sunlight works, the UV C isn't the important agent of change. > > At 12:14 PM 11/8/2007, you wrote: >>Thanks Chris >>I stopped using the window sill. I've been putting the lens in the >>sun when it's bright, but most of the time I've been using a BLB >>blacklight bulb. It's only UVA. I don't know which wavelength is most >>effective. I could buy a UVB suntan lamp but I won't spend the money. >>If what I'm doing doesn't work I'll just continue to shoot b&w with >>the lens and be very happy. >> >>Len >> >> >>On Nov 8, 2007, at 11:16 AM, Chris Saganich wrote: >> >>>I believe low-E glass coatings suppress infrared, either way those >>>coatings don't do much for UV. The UV you would need to reverse >>>the coloration would be quite a bit more then found on a >>>windowsill. About one month continuous 24/7 exposure would do the >>>trick. Best to get a UV lamp and a tinfoil lined box. >>> >>> >>>Chris Saganich, Sr. Physicist >>>Weill Medical College of Cornell University >>>New York Presbyterian Hospital >>>chs2018@med.cornell.edu >>>Ph. 212.746.6964 >>>Fax. 212.746.4800 >>>Office A-0049 >>> >>> >>>_______________________________________________ >>>Leica Users Group. >>>See http://leica-users.org/mailman/listinfo/lug for more information >> >> >>_______________________________________________ >>Leica Users Group. >>See http://leica-users.org/mailman/listinfo/lug for more information > > Chris Saganich, Sr. Physicist > Weill Medical College of Cornell University > New York Presbyterian Hospital > chs2018@med.cornell.edu > Ph. 212.746.6964 > Fax. 212.746.4800 > Office A-0049 > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > _______________________________________________ Leica Users Group. See http://leica-users.org/mailman/listinfo/lug for more information