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

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Subject: [Leica] OT: Fixing radioactive lenses
From: jhnichols at bellsouth.net (Jim Nichols)
Date: Wed Nov 7 19:09:38 2007
References: <27347376-1AD0-40B7-B526-32A6572F1A6D@comcast.net><200711072256.lA7MuoDn068946@server1.waverley.reid.org> <5B72DAE6-74AF-40C4-9FAA-0622EE820D3D@comcast.net>

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
> 



Replies: Reply from hoppyman at bigpond.net.au (G Hopkinson) ([Leica] OT: Fixing radioactive lenses)
Reply from len-1 at comcast.net (Leonard Taupier) ([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)