In video, what appears to be a continuously moving image is actually a series of
discrete still pictures, called frames. Each frame lasts 1/30 second each contains 480
scanning lines that appear on the screen. Because of limitations in the early days of
television, these 480 lines were divided into two "fields," each of which lasts 1/60 second.
The first field displays the odd-numbered scanning lines. The second field comes
back and displays the even-numbered scanning lines. This is "interlace" scanning and it
displays only 240 scanning lines at any one time. This system of 480-line interlaced
display is abbreviated "480i."
Interlace scanning (left) divides the frame into two "fields." The
first field presents the odd-numbered scanning lines (1, 3, 5, etc.).
The second field presents the even-numbered lines.
Progressive scanning (right) creates the picture by illuminating
each line from top to bottom until all scanning lines in the frame
are completed. Progressive images have twice the vertical
resolution, so they're noticeably clearer and sharper. And
horizontal scanning lines are far less conspicuous.
In the early days of television, when 12-inch diagonal screens were commonly
used in living rooms, showing only 240 lines was not a practical concern. But in today's
environment of 61-inch diagonal projection systems, the illusion of a continuous picture
on the screen begins to fall apart. Depending on how close to the screen you sit,
individual scanning lines become visible and the compromise in vertical resolution
becomes an annoyance. That's why most of today's finest DVD players and big screen
televisions have the ability to present a progressive scanning image. Instead of getting
240 lines, you get 480 lines every 1/60 second. This 480-line progressive scanning is
abbreviated "480p," and it delivers twice the vertical resolution of conventional video!
Connect a DVD player with progressive scan output to a "high scanning," "High
Definition monitor" or "High Definition upgradeable" television and the results are
phenomenal. You'll see images that are noticeably smoother and more film-like. It's less
like television, more like movies in a theater!
The Sony Guide to Home Theater
About Progressive Scan