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Fixing Pentax Super Takumar 50mm F1.4 "radiactive"
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PostPosted: Sun Oct 21, 2007 6:21 pm    Post subject: Fixing Pentax Super Takumar 50mm F1.4 "radiactive" Reply with quote

Seen on the net:

http://www.rangefinderforum.com/forums/showthread.php?t=47689

It shows how to cure the yellowish tint, not sure if radiactivity goes away as well or if it's innocuous.

Best regards,
Jes.


PostPosted: Fri Nov 09, 2007 9:10 am    Post subject: Reply with quote

Yes, this works.

The point is that over time the glas structure is changing.
There are rumours on the net that this has to do with radioactivity or rare earth elements. But this is not clear.

What is clear though is that it seems that UV light is changing the glas structure back to its original state.

It works better when you put the lens in front of the window glas, if possible, because the glas is blocking UV light.


PostPosted: Fri Nov 09, 2007 11:34 am    Post subject: Re: Fixing Pentax Super Takumar 50mm F1.4 "radiactive&q Reply with quote

Jesito wrote:
not sure if radiactivity goes away as well or if it's innocuous.


Just forget the radioactivity, c.f. http://hps.org/publicinformation/ate/q1356.html ,

and if you really want to know, here is the link

http://library.lanl.gov/cgi-bin/getfile?23-01.pdf

An interesting detail: some parts of the lungs of smokers get about 50 times the average annual total, i.e. 16000 mrem (based on 30 cigs a day, if I remember correctly, so one cigarette per day more than doubles the exposure.) Compared to this, these lenses are really negligible.

Veijo


PostPosted: Fri Nov 09, 2007 12:16 pm    Post subject: Reply with quote

Don't know this is need or not I have a Pancolar 1.4 55mm lens also with yellow glass this is normal for this lens I will not cure in any circumstances.
http://www.mflenses.com/gallery/v/german/zeiss/pancolar_001/carl_zeiss_jena_pancolar_55mm_f1_4/


PostPosted: Fri Nov 09, 2007 8:22 pm    Post subject: Reply with quote

blende8 wrote:
Yes, this works.

The point is that over time the glas structure is changing.
There are rumours on the net that this has to do with radioactivity or rare earth elements. But this is not clear.

What is clear though is that it seems that UV light is changing the glas structure back to its original state.

It works better when you put the lens in front of the window glas, if possible, because the glas is blocking UV light.


Hi, Blende8! Welcome to this forum.