They are discussing the *rear* lens node. A lens has two nodes . . . front
and rear. The effective location of the rear node is one focal length in
front of the film plane when the lens is focused at infinity.
A lens node is sometimes also referred to as a principle point . . .
although the strict definition for the two is different. However, if the
media in front and behind the lens is the same (i.e., same refractive
index), they are in the same location.
-- John
At 23:37 4/10/03, Lama asked:
Is the "lens node" always one-half of the focal length away from the film
plane?
Just wondering,
Lama
> This is not a true panorama head, or at least a very limited one, as it
> does not allow for placing the lens node over the rotation axis.
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