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[OM] Re: Yellow lenses [was: Forgot the URLs!]

Subject: [OM] Re: Yellow lenses [was: Forgot the URLs!]
From: alfredo pagliano <alfredo_pag@xxxxxxxx>
Date: Thu, 25 Aug 2005 21:20:17 +0200
mmmhhh

the second does seem a little too radical for my taste...

Even though I must admit this solution often temptes me when I have 
problems with the hardware...

On Aug 25, 2005, at 8:44 PM, Moose wrote:

> alfredo pagliano wrote:
>
>> Yellowish image due to the rare-earth glass element?
>>
>>
> Some of the earliest M and OM system 50/1.4 lenses and the first series
> of 55/1.2 lenses used a bit of a radioactive rare earth element in the
> glass of one or more elements. The long term effect of the radiation is
> that the elements turn slightly yellow. For color or B&W negative film,
> it doesn't make a significant difference. For slides, it does create a
> noticable color cast.
>
> Reports are that the radioactive 50/1.4s were sharper in the center 
> than
> the ones immediately following them. It didn't take long for other
> advances in optical glass and lens design to exceed these early lenses
> without rare earth components.
>
> The radioactivity was enough to easily register with a geiger counter,
> but not enough to fog even fast film left in the camera. I believe one
> of several threads in the archives in the last year or two talks about
> much more moderate radioactivity in a couple of other early lenses.
>
> Oly was not alone in this, There is a series of the Pent*x 50/1.4 
> famous
> for turning quite yellow. There are two reported cures for the Pent*x
> lens, letting strong UV light pour through it for an extended period or
> <http://www.hermes.net.au/bayling/repair.html>.
>
> Moose
>
>
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