Posted by Andrew Rossmann on 01/31/07 22:05

In article <D_6wh.832427$5R2.679581@pd7urf3no>, stuart_miller@shaw.ca
says...
>
> <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.

Don't confuse HORIZONTAL resolution with VERTICAL resolution.

525 is the VERTICAL resolution of NTSC. Of those 525, only 480 actually
carry picture information. The rest are for sync, closed captioning, and
other digital transmission features (parental control, XDS,
TVGuideOnScreen, timecode for VCR's, etc...)

The 240/330, etc mentioned above are rough HORIZONTAL resolutions.

For reference, the HD resolutions are:
1280(h)x720(v)
1920(h)x1080(v)

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