PanoTools:
Re: entrance pupil - nodal point
wardnet2001 2004-Nov-12 00:54:35
--- In #removed#, "Erik Krause" <#removed#> wrote:
> On 11 Nov 2004 at 17:55, wardnet2001 wrote:
>
> > But here's a request. I use a Sigma 8mm. Is it possible for someone
> > with the necessary knowledge to definitively state where exactly the
> > point of rotation is on this lens? Someone has already mentioned the
> > gold ring near the front, I use a point slightly forward of this. I
> > suppose Sigma would be the best to state where this is (wonder why
> > they dont).
>
> There is no well defined point for a fisheye. See here for a diagram
> how it changes with viewing angle:
> http://michel.thoby.free.fr/SIGMA8mm/Alpha%20test%20300D/Graph%20Beta.
> jpg
>
> best regards
> --
> Erik Krause
> Ressources, not only for panorama creation:
> http://www.erik-krause.de/
Hello Erik
Thanks very much for this very useful reply.
Looking at the diagram and taking into account the fact that in a
panorama comprising of 5 vertical photos the final image (for a 360'
panorama) consists of image pairs stitched together at their overlap,
ie at angles between (much) less than 90' and more than about 60',
then an "optimal" position for the point of rotation would indeed be
slightly forward of the gold ring.
Its interesting to realise that its actually therefore impossible to
have a point of rotation that will produce zero paralex error at all
points in the overlap between 2 overlapping images. It would be
neccessary to use one of the scanning panoramic cameras to produce
images free of paralex error. I hadnt undrstood this till now. Of
course we can still continue to make believable images.
Bill
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