Archived posting to the Leica Users Group, 2007/11/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Phillipe,
Just bring the two photos into Photoshop and anyalyze them
(difference layers). The first one clearly has a browner component
when the backgrounds cancel each other.
The light going through the lens is from the background as well, so
it doesn't matter that the actual lighting is exactly the same, as
long as the colour temperature and green-magenta balance are not
hugely different in the light source.
>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
--
* Henning J. Wulff
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