PanoTools:
Re: entrance pupil - nodal point
John Houghton 2004-Nov-10 09:59:52
If you move the entrance pupil, by putting a small aperture a short
distance in front of the lens, it is clear that this becomes the
centre of perspective. If you use the usual techniques for
determining "the nodal point", then it is the position of the
aperture that is found, NOT the nodal point, which hasn't changed.
(I have verified this). It is not clear to me that one can assume
that the positions of the nodal point and entrance pupil are
necessarily coincident, by accident or design, in modern complex lens
systems.
John
--- In #removed#, "Erik Krause" <#removed#>
wrote:
> On 9 Nov 2004 at 18:42, Milko Amorth wrote:
>
> > Entrance pupil - The "center of perspective" of the lens. It is
the
> > center of rotation for panoramic photography. Panoramic
photographers
> > sometimes refer to it as the "nodal point", but it's not. This
point
> > is the virtual image of the len's aperture.
>
> Not exactly true. In optical terms a 'virtual image' is f.e. what
you
> see if you are looking through a magnifying glass (which is exactly
> what happens if you look into a lens where the front lens group
forms
> a convex lens). In this case, the virtual image is always further
> away from the you than the object (thats why you see it larger). In
> almost all cases this is not the 'no parallaxe point'. If you say
the
> entrance pupil is the diameter of the virtual image of the
aperture,
> you're exactly right.
>
> [...]
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