PanoTools:
Re: entrance pupil - nodal point
David Sykes 2004-Nov-11 15:08:03
Rik Littlefield wrote:
> The entrance and exit pupils are often defined as images of the
> aperture as seen through the front and back lens elements. (This
> definition fails, by the way, for telecentric lenses, whose
entrance
> pupil is effectively at minus infinity.)
Not so !
The definition is exactly right and it is why the magnification of
the subject does not change even when out-of-focus (within small
limits, but still far greater than conventional lenses).
As Rik knows, I have a telecentric courtesy of Ebay.
I have just looked into the front of it and can see (when wearing my
glasses for distant vision) the entrance pupil at infinity.
Not sure if it is plus or minus infinity though :-)
David Sykes
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