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Re: Yellowing of radioactive lens elements....Re: [OM] 55/1.2

Subject: Re: Yellowing of radioactive lens elements....Re: [OM] 55/1.2
From: Mark Dapoz <md@xxxxxxxxxxxx>
Date: Sun, 10 Aug 2003 17:21:38 -0400 (EDT)
On Sun, 10 Aug 2003, Mark Marr-Lyon wrote:

> And to answer another question, the only Zuikos known to be radioactive 
> are the silvernose 55/1.2's, with 2 radioactive elements, and the very 
> early 50/1.4's, with one.  These are also the only known Zuikos to 
> yellow.  If your 55/1.2 is not a silvernose, then it's almost certainly 
> not radioactive.  There are silvernose 50/1.4's that are not 
> radioactive though, and the SN of the change has not been determined.  
> There are no radioactive 50/1.2's, and no known 50/1.8's.

Since I have quite a number of older Zuiko's, I decided to sample them and
see how their colour compares to newer versions.  I took each of the older
lens and placed it next to a newer version of the same lens.  Both lenses were
placed face down on a light table and the older lens element colour was
compared to the newer lens colour.  Here are the results:

Lens            Serial          Colour Cast
---------       -------         -----------
55mm f1.2       100584          severe yellowing
50mm f1.4       109257          minor yellowing
50mm f1.4       118622          minor yellowing
50mm f1.8       108622          no yellowing
50mm f1.8       114234          no yellowing
50mm f1.8       121253          no yellowing
35mm f2.8       103931          slight yellowing
35mm f2.8       108255          no yellowing
100mm f2.8      102159          slight yellowing

slight yellowing is a defined to be a bit more than minor yellowing.

What can we conclude from this?  Heck if I know, but I'm sure someone out
there will come up with some theories :-)  

The 55/1.2 is probably one of the earliest samples we're likely to find.
Just to show how you much yellowing has occured, I placed the lens in front
of a white background and snapped a photo of it.  It's actually yellower
in real life but this will give you an idea of what happens:
http://olympus.dementia.org/misc/55mm_yellowing.jpg

                                -mark



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