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Re: Parallax and zooming



At 22:31 9/16/97 EDT, you wrote:
....
A good experiment for some of us; I just tried it and got a confirmation.

Two vertical sticks in the plane parallel to the wall. They are separated
by about 20 cm from each other. Their distance from the wall also about
20 cm. And three thick lines on the wall (electric tape)...
I place the camcorder close to the sticks (its lens is 60 cm from them),
focus it manually and minimize zooming. The paralax is ALPHA (the width
of one stick) on each side. I move the camcorder to a distance of about six
meters from the sticks... The parallax is four to five times smaller...

How did you figure this out? Ludwik Kowalski

Perhaps you have watched a horse-race portrayed on TV.
It is distracting to find that the horses on the back-stretch appear
very nearly the same size as the nags on the home straight.
This is an associated effect of telephoto use at long distance.

As a practical matter, I hear that vehicle manufacturers find it
advantageous to take three-view photos at long distance with strong
telephotos to generate accurate outline data of their new models.


brian whatcott <inet@intellisys.net>
Altus OK