Archived posting to the Leica Users Group, 2007/11/08

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] OT: Fixing radioactive lenses
From: jhnichols at bellsouth.net (Jim Nichols)
Date: Thu Nov 8 12:16:39 2007
References: <27347376-1AD0-40B7-B526-32A6572F1A6D@comcast.net><6.2.1.2.2.20071108110103.015e33e0@pop.med.cornell.edu><2687855D-C773-4DB1-8C53-39461CBE170F@comcast.net> <6.2.1.2.2.20071108141526.014bfab0@pop.med.cornell.edu>

Chris,

You sure lost me!  I'm just happy that my 50/1.4 Takumar does not display 
the yellow cast.

Jim Nichols
Tullahoma, TN USA
----- Original Message ----- 
From: "Chris Saganich" <chs2018@med.cornell.edu>
To: "Leica Users Group" <lug@leica-users.org>
Sent: Thursday, November 08, 2007 2:08 PM
Subject: Re: [Leica] OT: Fixing radioactive lenses


> Well, I'm curious why it even works at all.  In a typical application 
> color is removed from glass by annealing or heating the glass at about 800 
> F for a short time and slowly cooling.  The time and temperature are the 
> main issues and a  look into glass annealing (ie gemstone and color center 
> activation) should shed some light.  Perhaps a slight elevation of 
> temperature for 24 hours?
>
> The UV wavelength for A and B are not high enough per se to cause a 
> redistribution of electrons in the atomic valence but UV C does have a 
> high enough wavelength.  The only problem is that is how the color is 
> activated in the first place, by kicking around electrons!  In order to 
> have the process reversed the UV and the glass must have broad energy 
> states in common to cause enough heat  absorption to weaken the existing 
> bonding allowing new lower energy bonds to form eliminating the number of 
> electron radicals in the mix.  Since UV C is more likely to ionize and 
> create electron radicals minimizing the UV C would seem like an idea. 
> Anyway UV C is filtered by the atmosphere so if leaving the lenses in the 
> sunlight works, the UV C isn't the important agent of change.
>
> At 12:14 PM 11/8/2007, you wrote:
>>Thanks Chris
>>I stopped using the window sill. I've been putting the lens in the
>>sun when it's bright, but most of the time I've been using a BLB
>>blacklight bulb. It's only UVA. I don't know which wavelength is most
>>effective. I could buy a UVB suntan lamp but I won't spend the money.
>>If what I'm doing doesn't work I'll just continue to shoot b&w with
>>the lens and be very happy.
>>
>>Len
>>
>>
>>On Nov 8, 2007, at 11:16 AM, Chris Saganich wrote:
>>
>>>I believe low-E glass coatings suppress infrared, either way those
>>>coatings don't do much for UV.  The UV you would need to reverse
>>>the coloration would be quite a bit more then found on a
>>>windowsill.  About one month continuous 24/7 exposure would do the
>>>trick.  Best to get a UV lamp and a tinfoil lined box.
>>>
>>>
>>>Chris Saganich, Sr. Physicist
>>>Weill Medical College of Cornell University
>>>New York Presbyterian Hospital
>>>chs2018@med.cornell.edu
>>>Ph. 212.746.6964
>>>Fax. 212.746.4800
>>>Office A-0049
>>>
>>>
>>>_______________________________________________
>>>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
>
> Chris Saganich, Sr. Physicist
> Weill Medical College of Cornell University
> New York Presbyterian Hospital
> chs2018@med.cornell.edu
> Ph. 212.746.6964
> Fax. 212.746.4800
> Office A-0049
>
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information
> 



Replies: Reply from joelct at singnet.com.sg (Joseph) ([Leica] OT: Fixing radioactive lenses)
In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] OT: Fixing radioactive lenses)
Message from chs2018 at med.cornell.edu (Chris Saganich) ([Leica] OT: Fixing radioactive lenses)
Message from len-1 at comcast.net (Leonard Taupier) ([Leica] OT: Fixing radioactive lenses)
Message from chs2018 at med.cornell.edu (Chris Saganich) ([Leica] OT: Fixing radioactive lenses)