Re: optics data

"Tony Williams" <[EMAIL PROTECTED]> wrote in message
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> "Dirk Bruere at Neopax" <[EMAIL PROTECTED]> wrote in message
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> > "Matteo" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> > > About optics used on rifle, what does the data numberXnumber mean?
> > > For example in "Trijicon ACOG 4X32 Day Optic" I suppose that the first
"4"
> > > is the zoom factor, but what about "x32" ?
> >
> >
> > Diameter of the major lens in mm
>
> Some further information: dividing the objective lens diameter by the
> magnification provides the 'exit pupil' diameter: so for the 4 x 32
> this is 8mm. The wider this is, the easier it is to use the sight and
> the brighter the image will be in poor light. The pupil of the eye
> varies in size between about 3.5mm in daylight and 7mm at night. So in
> daylight, a scope with 3.5mm exit pupil will be as bright as anything,
> but as the light falls the eye's pupil expands and can make more use
> of the larger exit pupil of the scope.

Which reminds me of something I should know, but I never liked doing optics
on the physics course...
Is it possible to build a light intensifier of arbitrary power simply by
expanding the dia of the objective and keeping the magnification low?

-- 
Dirk

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