Archived posting to the Leica Users Group, 2007/11/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Joseph, I have never been sure how to distinguish the lens model. My lens is engraved Super-Multi-Coated TAKUMAR 1:1.4/50 and the SN is 5720518. Also, ASAHI OPT. CO., JAPAN. On the back of the Manual/Auto slide is the number 37902. If you can enlighten me as to its characteristics, I would very much appreciate it. Jim Nichols Tullahoma, TN USA ----- Original Message ----- From: "Joseph" <joelct@singnet.com.sg> To: "'Leica Users Group'" <lug@leica-users.org> Sent: Friday, November 09, 2007 9:22 AM Subject: RE: [Leica] OT: Fixing radioactive lenses > 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 > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >