TV Screen Sizes (slightly OT) 2004-02-17 - By Alain
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Jason Lechak wrote:
>
> 720P means, 720 columns of resolution, P means, progressive scan. 1080I
> means, 1080 columns of horizontal resolution, and I means, interlaced.
> Progressive scan gives you a clearer picture, because both the odd and
> even
> horizontal screen lines are redrawn with each screen refresh. Interlaced
> means, in one screen refresh, all the odd lines are refreshed, then in
> the
> next refresh, the even lines are refreshed. This is the old way of
> refreshing TV video, because back in the olden days TV systems were not
> fast enough to refresh the entire screen each time. This is quite similar
> to PC monitor refresh rates and terminology.
That's actually slightly inaccurate.
A 30 frames per second system has the same bandwidth of a 60 fields per
second one.
It was not that the TVs were not fast enough to display 30fps but the
fact that older TV screen phospohors had a higher latency than those
found in today's TV sets. In order to get a clear picture without
strobing effects, the phospohors had to be allowed to react so instead
of sweeping the screen's every line 30 times per second, they do every
other line 60 times per second. (BTW, it's actually 29.97 times per
second and 59.94 Hz)
Salutations!
-Alain Bellon
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