T3D Re: Where?

[John Bercovitz <bercov@xxxxxxxxxxx>]

> Would the front principal point, then, be an image of the aperture stop???

They're actually different things - one's the principal point and
the other's the pupil (entrance pupil, in this case).  However, in
a symmetrical lens, they're coincident.  It's only when one lies
a long distance from the other along the optical axis that things
get complicated.  By a long distance, I mean a long distance compared
to the distance from the camera to the object.  For a less fuzzy
definition, see the paper Tom Deering put up for us on his web site.

John B


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