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'Digital Zoom on Video Cameras'
1999\03\11@075216 by Jim Dolson

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Does anyone know how the new video cameras do their digital zooms?
Instead of changing the focal length of the lens, I assume they bit-bang
the video somehow.  Any ideas?  Has anyone seen a web-site with a
description of the process?  Would a PIC be up to the task?

Just thinking about a project ...

Thanks,

Jim
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1999\03\12@015844 by Nigel Goodwin

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In message <.....36E7BC26.AB8CE056KILLspamspam@spam@iserv.net>, Jim Dolson <jdolsonspamKILLspamISERV.NET>
writes
>Does anyone know how the new video cameras do their digital zooms?
>Instead of changing the focal length of the lens, I assume they bit-bang
>the video somehow.  Any ideas?  Has anyone seen a web-site with a
>description of the process?  Would a PIC be up to the task?

I can't say I've actually seen anything about it, but I've always
assumed it just reads from a smaller portion of the CCD - rather like
zooming in on a paintbox programme. I presume that the resolution
suffers when you do this!.

I also presume the anti-jitter works in the same way, as the image moves
about the CCD, move the scanned 'window' to follow it.

BTW, the digital zoom is used in conjunction with the normal focal
length zoom, it only comes into play at the higher zoom settings - thus
giving a much higher zoom range.
--

Nigel.

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1999\03\12@112507 by John Payson

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I also presume the anti-jitter works in the same way, as the image moves
about the CCD, move the scanned 'window' to follow it.

There are three styles of anti-jitter systems:

[1] Examine the image, frame-by-frame, and judge whether the camera
   is moving based upon the image; move the image around electronic-
   ally based on that.

[2] Use a gyroscopic sensor to detect camera motion, and move the image
   around electronically based on that.

[3] Use a gyroscopic sensor to detect camera motion, and move the image
   around optically using moveable mirrors based on that.

In addition, there's a method which was (probably still is) used on
some professional movie cameras:

[*] Have the camera mechanism "floating" in a gimballed subsystem within
   the device the user holds, so that small changes of angle on the
   handgrips won't change the angle of the camera.

Of the common choices for camcorders, [3] is the most expensive, but it
avoids some of the motion-blur problems that can result from [2].  [1]
avoids mechanical sensors, but detecting what motion is real isn't always
easy or reliable.

1999\03\13@093158 by Marc

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> avoids some of the motion-blur problems that can result from [2].  [1]
> avoids mechanical sensors, but detecting what motion is real isn't always
> easy or reliable.

Definately - thinking of a car passing by, covering most of the visible area
the camera sees for a moment. :-)

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