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Re: Taylor-Merchant stereoscope lenses
- From: P3D John Bercovitz <bercov@xxxxxxxxxxx>
- Subject: Re: Taylor-Merchant stereoscope lenses
- Date: Tue, 6 Aug 96 14:47:28 PDT
>>>your face. Noticeable chromatic abberation, too. So glass
>>>lenses are yet another item on that wish list of mine
>>Are you saying that plastic lenses necessarily have more chromatic
>>aberration than glass lenses?
>Dunno about that...John?...for "glass lenses" please substitute
>"Red Button or equivalent." :-)
I'll have to look it up (books are at home) but I think ordinary
optical plastic has a littler more dispersion than ordinary optical
glass. At least for lenses of equal power (not equal curvature).
Since OCC is tonight, I probably won't get a chance to look it up
until tomorrow night.
The problem is power. I doubt it would be much of a problem in
a low power lens of reasonably small diameter. 5 diopters is not
exactly low power but it ain't 10 or 20 diopters where you'd really
see it. The problem occurs when you look through the edge of a
lens instead of through the center of it. I think the lens centers
in a stereoscope are about 90 mm apart so you're bound to look through
the edges of the lenses if your eyes aren't also 90 mm apart. 8-)
With an expensive mold, you can mold good plastic lenses but you
can't mold good glass lenses as far as I know. So the plastic
lenses are cheaper in quantity.
John B
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