Автор: ddimo
Дата: 23-09-07 00:00
Е това е от първия линк в Вики-то:
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DETERMINING THE LOCATION OF THE ENTRANCE PUPIL
Published tests
Many publications on panoramic photographic techniques (the same ones that
wrongly tell us that the proper pivot point is “the nodal point” of the lens) describe
practical tests for finding the location of “the nodal point”. Are these tests useless
to us, given that we need to know the location of the entrance pupil?
Not at all. Most of these tests actually determine the location of the entrance pupil!
...
Visual determination
In most cases, we can make a sufficiently-accurate determination of the location of
the entrance pupil by just looking at it. Recall that what appears to us to be the
aperture stop when we look into the front of the lens is actually (by definition) the
entrance pupil. Of course, what we see is just a “mirage”, but that’s what the
entrance pupil is when the aperture stop is inside the lens—a virtual image. Do not
be concerned by the fact that you can’t tell from in front of the lens exactly where
the physical aperture stop itself is—that’s not what we are interested in, just where
it looks like it is.
The first task is to be sure which of the various circular outlines we see when
peering into the lens is actually the entrance pupil. If the camera provides a way to
stop down the aperture, that will of course make it immediately clear which is the
correct feature. On a single lens reflex camera with a depth of field preview button,
set the aperture to a moderate value and, while looking into the lens, press the
button. You will see the entrance pupil get smaller.
Then judge its apparent “depth” from the front of the lens. This is then the location
of he entrance pupil.
Variation of the location with lens adjustments
Note that the location of the entrance pupil may change with focal length setting
(on a zoom lens) and even with focus setting (depending on the focus system that
is used). The change will ordinarily be small, and such small changes should not be
a matter of great concern.<<
http://doug.kerr.home.att.net/pumpkin/Pivot_Point.pdf
Мързи ме точно сега да го превеждам, ама на тоя пич, който явно е писал и статията във Вики-то, така му е замотана терминологията, че думи нямам направо![[smilie2]](https://photo-forum.net/forum/smileys/smilie2.gif)
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