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Re: [OM] Lens test loan request

Subject: Re: [OM] Lens test loan request
From: Gary Reese <pcacala@xxxxxxxxxxxxx>
Date: Wed, 28 Mar 2001 20:47:05 -0800
Winsor C. asks:

re: using rare earth (radioactive) glass in photographic lenses

<< is that way of making glass something that has come and gone? >>

Check this out, which was just posted on the Canon FD list:

<< This is off topic now (sorry!) but I thought I'd mention that a few
makes of telescope eyepiece have brought lanthanum back into style,
though the yellow colour cast we 35mm f/2.0 concave lens-lovers know
well is often mentioned as a drawback.  They are mainly used in long
eye-relief and wide-angle optical solutions, the same applications used
by the military in tank gunner sights, etc.

Funny for something people were worried about -- an eyepiece is used
much closer than your average camera lens. >>

I added that the viewfinder in early Pentax 67 cameras really spikes a
Gieger counter.

I have no knowledge of what glass now offers the same extra low
dispersion characteristics as the old thorium and lanthium glass, but it
is obviously free of color casts.

Gary Reese
Las Vegas, NV




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