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Posted by Jeff Rife on 04/15/06 03:56
Gene E. Bloch (spamfree@nobody.invalid) wrote in alt.tv.tech.hdtv:
> I took the lens elements out of a Wollensak Rapax leaf shutter (almost
> as old as I am) so I could look through it at several LCD devices (an
> LCD TV, a desktop monitor, and a laptop monitor) and one CRT device (a
> TV). I triggered the shutter at 1/400 sec while looking towards each of
> the respective screens in turn.
>
> On the CRT TV I saw a fraction of a picture (a horizontal band taken
> from the whole). The band was in a different location each time,
> because I couldn't synchronize my trigger finger with the vertical
> pulse :-)
>
> In each LCD device I saw the entire picture every time. Every time.
> Always. On the LCD TV, that was true for both standard def an high def.
This will *always* be true with such a fast shutter speed. It takes
an LCD element 1/30th of a second to change from one state to another.
At 1/400 of a second, you will always see what appears to be the same
frame.
A CRT progressively-scanned at 60Hz with a phosphor that took 1/30th of a
second to decay would result in the same image as on an LCD. Do the
math for a moment to figure out why.
--
Jeff Rife |
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