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Posted by Gene E. Bloch on 04/17/06 22:46
On 4/16/2006, Jan B posted this:
> (Sorry I had to work around a FreeAgent limit by move the follow up upwards
> in the thread).
>
> On Sat, 15 Apr 2006 09:45:05 -0400, Tom Stiller <tomstiller@comcast.net>
> wrote:
>
>> In article <4440e4d2.109134196@news.individual.net>,
>> nospam@nospam.se (Jan B) wrote:
>>
>>> When such a camera pans horisontally over a vertical object like a
>>> pole and the video is displayed on a CRT that takes nearly a field
>>> period to scan from top to bottom I would expect to perceive a tilted
>>> object "moving" across the screen. This is since the scanning at the
>>> bottom would lag the top when displaying but not at the recording.
>>>
>>> Have anybody noticed such effects?
>>
>> You overlooked the effect of the electronic shutter that effectively
>> freezes the image before it is scanned out. There is no relative motion
>> during the scanning process.
>
> But that is excactly my point. The case cited above is the case with freezed
> momentary picture in the CCD-camera, but the scanning in the CRT takes time.
> To get a smooth "momentary strobed" motion over the CRT surface, the camera
> picture should be scanned the same way (I think).
>
> The "moving" vertical pole should have moved to a later position when the CRT
> scans the bottom lines.
> /Jan
The CRT doesn't scan anything, it just displays what the signal says.
In this case, the signal says the pole is straight.
HTH,
Gino
--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")
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