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Re: Another camera question



Some of them use a contrast sensor, a light sensitive surface in the
image plane that seeks maximum contrast in the image. When the camera
is out of focus, the image is fuzzy and contrast is reduced. I think
this is what is referred to when you see that a camera uses "passive
autofocussing." Some also do the same thing using IR imaging,
presumably because most people take pictures of other people and
would like them to be in focus, not the surroundings. I haven't the
foggiest how you might construct a contrast sensor however. I suppose
you try to maximize the number of pixels which exhibit a major change
from neighboring pixels.

How do the automatic focusing cameras focus? (I don't mean the sonic
rangefinders)
I've wondered about this for a while, and now I see it mentioned in the
"Path of Light" discussion, so someone out there should be able to
explain it!
--
Martha Takats

Paul J. Camp "The Beauty of the Universe
Assistant Professor of Physics consists not only of unity
Coastal Carolina University in variety but also of
Conway, SC 29528 variety in unity.
pjcamp@coastal.edu --Umberto Eco
pjcamp@postoffice.worldnet.att.net The Name of the Rose
(803)349-2227
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