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, I have a color photo in my LUG gallery that was made with my 50/1.4 Takumar and a 2x extender. It is a true closeup against an out of focus background, and I can't see any distraction from any supposed discoloration. The individual from whom I purchased the lens said he only used it for B&W because he thought color would be affected. I just can't see it. The link is shown below. Today, I rescanned the negative and searched for any trace of a problem, and I couldn't distinguish between this one and the original lab scan. See what you think. http://gallery.leica-users.org/v/OldNick/Fuchsia_Blooms_sm.jpg.html Jim Nichols Tullahoma, TN USA ----- Original Message ----- From: "Leonard Taupier" <len-1@comcast.net> To: "Leica Users Group" <lug@leica-users.org> Sent: Wednesday, November 07, 2007 7:20 PM Subject: Re: [Leica] OT: Fixing radioactive lenses > Hi Marc, > > Actually it's not important that I remove the faint yellow of this lens > because it will not affect the b&w photos I plan on taking with it. But > it's been documented a few times that the yellow cast is considerably > diminished after about two weeks exposure to sunlight or a UV lamp. > Actually the lens is a curiosity to me. If the process works I've > accomplished two things, one prove the fix works and two I can take color > photos with a supposedly very good lens. Also I'm a little leery about > taking lenses apart. I'll take apart a car, a TV set or a computer, but a > lens or a camera, nope. > > Regards, > Len > > > > On Nov 7, 2007, at 5:54 PM, Marc James Small wrote: > >> At 05:10 PM 11/7/2007, 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. >> >> Len >> >> I love you like a brother, but be conscious here. The yellow cast may >> well result from decaying coatings. Disassemble the lens, remove the >> lens coatings, and then contemplate the result. If an element is >> yellow, then, yes, your original thesis may be correct. >> >> It takes thousands of years for radioactive elements to decay. I am >> baffled at the thought that the passage of only a few decades can lead >> to some change in the color of glass elements. Maybe I am a babe in the >> woods -- you guys have locked my heels over the years on things ranging >> from the utility of Tilley hats to the vibrant necessity of US >> television -- but I just do not see this as change as a reality. >> >> Do we have any nuclear chemists on the List who can add anything to the >> discussion? Jerry Lehrer, I realize, will tell us of his experience at >> the Brooklyn Home For Broken Boys or whatever it is called, back in 1921 >> <he grins>, but I really would like to know the straight skinny from >> guys who regularly have worked with thorium or with thorium glasses. >> >> And, Jerry, you STILL owe me those promised serial numbers from your >> studio Rollei. <he grins, yet again> >> >> In short: can Thorium glass really change color in a few decades? We >> hear this all the time. But is it real? >> >> Marc >> >> >> msmall@aya.yale.edu >> Cha robh b?s fir gun ghr?s fir! >> >> >> >> _______________________________________________ >> 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 >