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, Thanks for the comments. I also have another Takumar, an SMC 55/1.8, and it has no signs of yellowing, either. For my money, we should just use them and forget the legacy stories. 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 9:23 PM Subject: Re: [Leica] OT: Fixing radioactive lenses > Jim, > > That's a beautiful photo. I don't think you have the yellow problem. Your > lens is newer then mine and may not have the Thorium. I read that Pentax > may have eliminated it when they started making the Super Multi Coated. > They both have the same performance. I also have a 50/1.8 Super Multi > Coated that has no yellow tint at all. > > Len > > > On Nov 7, 2007, at 10:09 PM, Jim Nichols wrote: > >> 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 >> >> >> >> _______________________________________________ >> 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 >