PanoTools:
Re: entrance pupil - nodal point
Erik Krause 2004-Nov-12 14:22:02
On 12 Nov 2004 at 2:19, Rik Littlefield wrote:
> > Yes, for a rectilinear lens this is absolutely true.
> > For a fisheye it is not, since the focal length (and hence
> > all the optical geometry) depend on the viewing angle.
> > If your fisheye has 8mm focal length, this is only true
> > for the center. The focal length gets smaller to the edges
> > and is virtually zero at the very edge of the image circle.
> > Otherwise it would not cover 180° field of view (or more).
>
> But for a fisheye, the plane containing the entrance pupil moves
> forward if you view from off-axis. All I am saying is that the
> center of perspective (the no-parallax point) for an off-axis angle
> still corresponds to the plane of the entrance pupil, in its new
> position closer to the front of the lens as seen from that angle. I
> do not see where a change in effective focal length challenges this
> interpretation.
I do not fully understand what you mean with your last sentence, but
you can find some facts on fisheye geometry here:
http://www.a1.nl/phomepag/markerink/fishyfaq.htm
Especially the contribution of - who is surprised? - H. Dersch...
best regards
--
Erik Krause
Ressources, not only for panorama creation:
http://www.erik-krause.de/
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