Archived posting to the Leica Users Group, 2007/11/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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