PanoTools:
Re: entrance pupil - nodal point
Dave 360texas.com 2004-Nov-13 01:35:07
Hmmm well this is a prime lens Nikkor 50mm. Not a variable zoom
lens.
--- In #removed#, "Erik Krause" <#removed#>
wrote:
> On 12 Nov 2004 at 20:50, Dave 360texas.com wrote:
>
> > When viewing though the 8mm FC-E8 fisheye glass front at my
pointed
> > up pencil is also pointed up.
>
> This one is an adapter. It only changes field of view for the lens
it
> is mounted on and in technical terms it is a concave lens which
never
> reverses the image. The lens it is mounted on reverses the image
like
> *any* photographic lens.
>
> > When viewing through my Nikormat film SLR 50mm 1:1.4 lens, at my
> > pointed up pencil - the image is point down. meaning that the
image
> > is inverted somewhere inside the lens, most likely at the iris
> > mechanism set at F16.
>
> This is the usual point where the lens constructor places the iris
> because this is the only point where the iris don't cause
vignetting.
> The iris can be placed at any other point without changing optical
> geometry (and in fact is often in zoom lenses, because the point
> where the center rays cross the optical axis moves while
zooming).
>
> best regards
> --
> Erik Krause
> Ressources, not only for panorama creation:
> http://www.erik-krause.de/
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