Mark Lloyd writes:

BTW, do you know how many lines a NTSC picture actually has? It's LESS
than 480.

What do you think the number is?

All NTSC signals have at least 480 scan lines no matter what the source.
The useful *vertical* resolution is about 70% of that due to something
called the Kell factor, again pretty much without regard to the source.

On the other hand, different NTSC sources have different *horizontal*
resolution figures, which are quoted in terms of "lines per picture
height" that can be resolved. Here, resolution is proportional to
analog bandwidth, and can be as low as 250 lpph for VHS, up to about 550
lpph for professional gear. But the horizontal resolution has no direct
connection to the "480 lines" of the format which is a vertical
measure.

Yes. The problem seems to be in the omitted middle. To help explain, I
will mention three things he

1. NTSC. Ordinary analog video as we've had since World War II.

There is a huge range in quality depending on the source (VHS, over the
air, laserdisc, DVD). These are all 480-line format, but horizontal
resolution varies. There's also a large difference in the colour
resolution between composite and component connections.

2. 480-line video, as with a DVD player connected with a YUV or HDMI
output. Still not HD.

This is a specialized subset of #1, with the image stored digitally at
704x480 pixels, and fed to the monitor either digitally or in analog
component form. It's still 480-line format, but horizontal resolution
is about 500 lines per picture height (for 4:3, less for widescreen).

3. HD: 720p / 1080i or greater.

Now you're getting greater horizontal *and* vertical resolution, and
possibly better temporal resolution too (in the case of progressive
scan).

You said that #3 was much better than #1.

I said that most of this difference was between #2 and #1, rather than
between #3 and #2.

This is sort of meaningless since #1 is a bucket that contains such a
huge range of quality. If your #1 source is a VHS tape running at SLP
speed, any DVD will be much better. If your #1 source is a laserdisc,
it's going to be pretty close to the DVD in quality despite being
composite analog.

To make a comparison that everyone might be able to agree with, you'll
need to be more specific about what kind of analog video you're
comparing against as #1.

Dave