PanoTools:
Re: entrance pupil - nodal point
Dave 360texas.com 2004-Nov-13 00:01:27
The significance of this image invertion in 50mm lens observation is
that most likely the aperature iris diahphram location inside the
lens is most likely the position of the rotation nodal point. Nikon
usually is quite accurate in identifying this point by placing a
gold or aluminum ring at this location.
Dave
--- In #removed#, "Dave 360texas.com"
<#removed#> wrote:
>
> As a matter of interest I also found this:
>
> When viewing though the 8mm FC-E8 fisheye glass front at my
pointed
> up pencil is also pointed up.
>
> 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.
>
> Interesting.
>
> --- In #removed#, "Dave 360texas.com"
> <#removed#> wrote:
> >
> > Ok..
> > It only has an entrance and exit pupil through which ALL light
> must
> > pass before arriving at iris aperture physically located inside
> the
> > camera head at least 5 cm behind the rotation point.
> >
> > In this instance, this fisheye lens is acting only as a THICK
> > complex LENS as the image is not inverted until it is inside the
> > camera head.
> >
> > Image 3 This thick lens behaves according to your Higher Physics
> > text book definition
> >
> > Image 3 http://360texas.com/images/lensangle.jpg
> >
> > Dave
> >
> > --- In #removed#, "Erik Krause"
<#removed#>
> > wrote:
> > > On 12 Nov 2004 at 18:19, Dave 360texas.com wrote:
> > >
> > > > Image 2. The next picture is of a fisheye with no iris or
> > aperature
> > > > with groups of optics which channel the incoming light
rays.
> It
> > > > appears that the image is inverted about mid center of the
> lens.
> > > >
> > > > I suspect that the point where the image is inverted is a
> nodal
> > > > point.
> > >
> > > No. It is the point for the best location of the iris
aperture.
> In
> > > this diagram you can see very good that there is no exact
nodal
> > > point. You find the nodal point for any viewing angle if you
> > lengthen
> > > the direction of the light rays outside the front lens to
where
> > they
> > > cut the optical axis. It is easy to see that this point moves
> with
> > > the angle of view.
> > >
> > > best regards
> > > --
> > > Erik Krause
> > > Ressources, not only for panorama creation:
> > > http://www.erik-krause.de/
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