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Posted by Stuart Miller on 01/31/07 20:29
<SFTVratings_troy@yahoo.com> wrote in message
news:1170274597.382084.36170@k78g2000cwa.googlegroups.com...
> For comparison other standards are:
> 240 - VHS (ditto Betamax)
> 330 - NTSC broadcast
> 425 - laserdisc (ditto S-VHS)
> 540 - DVD
>
> I was a bit surprised, but apparently the Electronics Industry
> Association measures the resolution differently than one might
> expect. They put a giant circle in the middle of the screen, count
> the number of visible pixels across, and arrive at a number like "425
> for laserdisc" or "540 for dvd". It seems counterintuitive, but
> that's how it's done.
>
> I imagine if the DVD is severely compressed, the quality would drop
> much lower than 540 (just as a VHS tape recorded in super-slow mode is
> only ~120 across). 540 is the ideal, not the norm.
>
Even in optimal situations, there are two resolutions to consider.
First is the signal. I had understood NTSC to be 525 each way, (for a video
camera)
Second is the display - there are regions of the signal ( top & bottom)
which are not displayed on the screen
So what you actually see is less than what is recorded. The technical
sections of sites like digitalfaq explainm this properly.
Stuart
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