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Standard Definition (SD) versus High Definition (HD)
The difference between SD and HD is not only the pixel count, but also
the frame size. Be aware of the aspect ratio during production.
Today, though most new video cameras are High
Definition (HD) capable, Standard Definition (SD)
is still typical for video production. This is because
DVDs for distribution use the SD format. Also, SD
provides acceptable video quality for projecting at
the venue.
However, we are now in a transitional period and
equipment is available in both formats. This can
cause confusion when building your system. If you
mistakenly show a video with an incorrect aspect
ratio on a 16:9 screen, people will appear wider.
Let's discuss a few points about SD and HD.
First of all, SD and HD have a different resolution
(pixel count). The SD screen contains 640×480 (or
720×480) pixels, while HD contains 1920×1080 (or
1440×1080, 1280×720). The aspect ratio of SD is
4:3 while HD is 16:9.
When filming with an HD camera to be displayed
on an SD screen, there are three methods to deal
with aspect ratio, as shown on the right. Insert black
margins on the top and bottom, which is called
letterbox; squeeze from both sides; or crop the left
and right edges, which is called edge crop. Some
HDV video cameras allow you to film with an aspect
ratio of 4:3. In any case, you should set a consistent
aspect ratio from the camera, to final recording, to
projection.
You can create a 16:9 wide DVD package if the
final format is DVD. Viewers with high definition TVs
can fully enjoy them on their wide-screen TVs. It is
possible to use the squeeze technique from filming,
to video mixing and final recording.
The risk is higher on location than in the editing
room where you have more time to think. The safer
approach is to maintain an aspect ratio of 4:3 for
SD and 16:9 for HD.
Nowadays, projectors are multifunctional and accept
signals from computers, DVI and HDMI. Some venue
projectors now use 16:9 panels. Be careful to avoid
confusion with aspect ratios.
036
■SD and HD have different aspect ratios
4
SD
16
HD
■Three methods to show HD on SD screens
HD
Letterbox
Squeeze
SD
Edge Crop
3
9
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