Archived posting to the Leica Users Group, 2007/11/10

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Subject: [Leica] Img: Radioactive lens fix works
From: len-1 at comcast.net (Leonard Taupier)
Date: Sat Nov 10 09:31:26 2007
References: <86E01E09-09CE-4A4A-A35C-A8DCA6E7DD5B@comcast.net><889076F9-8162-4953-B151-D511A0166969@pandora.be> <2EC67DDA-E55A-474A-84A4-295C9A110C15@comcast.net> <005301c823be$2f2b3ba0$6101a8c0@jimnichols>

Jim,

I don't know when they stopped using it. If I find out I'll let you  
know. Your lens could have been made only a year after mine.

Len


On Nov 10, 2007, at 12:21 PM, Jim Nichols wrote:

> Len,
>
> Your results in getting the yellow out are impressive.  My lens may  
> look a little darker than your final photo, but not much.  Do you  
> know how far down the model lineup the Thorium element was used?
>
> Jim Nichols
> Tullahoma, TN USA
> ----- Original Message ----- From: "Leonard Taupier"  
> <len-1@comcast.net>
> To: "Leica Users Group" <lug@leica-users.org>
> Sent: Saturday, November 10, 2007 11:02 AM
> Subject: Re: [Leica] Img: Radioactive lens fix works
>
>
>> Hi Philippe,
>>
>> Both photos were taken in natural window light but I see a slight  
>> difference in the color temperature. I can see the lightening of  
>> the color quite easily in any light though. It has been overcast  
>> here the last couple of days but Tuesday will be a sunny day and I  
>> plan on  taking some color slide photos then.
>>
>> Len
>>
>>
>> On Nov 10, 2007, at 11:52 AM, Philippe Orlent wrote:
>>
>>> Len,
>>> Impressive. And I believe you ofcourse.
>>> But I don't know if those photos prove your point. Both seem to  
>>> be  taken in different lighting situations so is there much  
>>> interest in  comparing them?
>>> Philippe
>>>
>>>
>>>
>>> Op 10-nov-07, om 17:21 heeft Leonard Taupier het volgende  
>>> geschreven:
>>>
>>>> For those of you interested in the Pentax 50mm yellowing  
>>>> problem,  Here are photos taken before and after 116 hours  
>>>> exposure to UV  light to reverse the yellow cast problem due to  
>>>> the radioactive  element Thorium in one of the lens elements.
>>>>
>>>> Before photo. Lens has brownish, yellow cast.
>>>>
>>>> <http://gallery.leica-users.org/v/LeonardT/Pentax/  
>>>> Takumar_50_2.jpg.html>
>>>> <http://tinyurl.com/233emd>
>>>>
>>>> Here is a photo taken after only 116 hours of being exposed to  
>>>> UV light. The exposure was to 16 hours of sunlight and 100 hours  
>>>> of  UV from a blacklight.
>>>>
>>>> <http://gallery.leica-users.org/v/LeonardT/Pentax/  
>>>> Takumar_116hrs.jpg.html>
>>>> <http://tinyurl.com/2bx7do>
>>>>
>>>> I did not expect any improvement this quickly if at all. I'll   
>>>> probably keep the lens in front of the blacklight for a few  
>>>> days  more to see if there is any further improvement.
>>>>
>>>> Thanks for your interest.
>>>> Len
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> 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
>
>
>
> _______________________________________________
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In reply to: Message from len-1 at comcast.net (Leonard Taupier) ([Leica] Img: Radioactive lens fix works)
Message from philippe.orlent at pandora.be (Philippe Orlent) ([Leica] Img: Radioactive lens fix works)
Message from len-1 at comcast.net (Leonard Taupier) ([Leica] Img: Radioactive lens fix works)
Message from jhnichols at bellsouth.net (Jim Nichols) ([Leica] Img: Radioactive lens fix works)