Archived posting to the Leica Users Group, 2007/11/07

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Subject: [Leica] OT: Fixing radioactive lenses
From: len-1 at comcast.net (Leonard Taupier)
Date: Wed Nov 7 19:23:55 2007
References: <27347376-1AD0-40B7-B526-32A6572F1A6D@comcast.net><200711072256.lA7MuoDn068946@server1.waverley.reid.org> <5B72DAE6-74AF-40C4-9FAA-0622EE820D3D@comcast.net> <027201c821b4$d7d8f910$6101a8c0@jimnichols>

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
>
>
>
> _______________________________________________
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> See http://leica-users.org/mailman/listinfo/lug for more information



Replies: Reply from jhnichols at bellsouth.net (Jim Nichols) ([Leica] OT: Fixing radioactive lenses)
In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] OT: Fixing radioactive lenses)
Message from marcsmall at comcast.net (Marc James Small) ([Leica] OT: Fixing radioactive lenses)
Message from len-1 at comcast.net (Leonard Taupier) ([Leica] OT: Fixing radioactive lenses)
Message from jhnichols at bellsouth.net (Jim Nichols) ([Leica] OT: Fixing radioactive lenses)