PanoTools:
Re: entrance pupil - nodal point
Erik Krause 2004-Nov-12 18:38:06
On 12 Nov 2004 at 14:21, John Houghton wrote:
> > What you show here is the example of a pinhole camera. If you follow
> > the light rays further to the right, you would see that there is only
> > one rotational position of the lens, where A and B are together on
> > the film - the position where A, B and N1 are on the same straight
> > line. Such a narrow aperture in front of the lens simply limits the
> > field of view...
>
> Erik, Of course there is only one position where A and B are in line
> when you rotate about the nodal point. This is why it is the wrong
> point to choose for the no parallax point. The example is no more a
> pinhole camera than any lens stopped down to f/16. The light rays
> get refracted by the glass just the same. The aperture certainly
> limits the field of view, but I still get a full image with such an
> aperture in front of a 50mm lens on my D60.
You're right with your experiment, since you get a projection of the
hole in front of your lens as a circle of confusion (as is the case
for any aperture). But see what happens if you focus to the
previously out of focus object - The objects move away from each
other...
It makes a difference whether the aperture is inside the physical
lens or outside. If it is inside you must calulate with it's
projection (what is called 'virtual image' by dan) not with the
actual physical location.
best regards
--
Erik Krause
Ressources, not only for panorama creation:
http://www.erik-krause.de/
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