Nikon D300 User Manual page 233

You have three choices available:
along with two SD modes,
numbers following the resolution
3:2—are format sizes.
will display on an SDTV in the wide-screen format, with a
black band on the top and bottom of the screen.
closely matches the SDTV
format (regular TV) we've been using for years, but which is
rapidly becoming obsolete.
normal TV. The HD format (1280×720) has a limit of 5
minutes recording time. The other two SD formats can record
20-minute video clips.
Figure 3-58. D-Movie mode – Quality
Here are the steps to choose a
1. Continuing from
settings), select
and scroll right (see
2. Select one of the three formats for video recording.
3. Press the
16:9
3:2
Figure 3-57
Quality
Figure
OK button to choose the format.
1280×720
640×424 and 320×216. The
numbers—16:9
is the standard HD format and
will display full-screen on a
Quality setting:
(Shooting Menu > Movie
from the Movie settings
3-58).
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(or 720p HD),
and
3:2 more
menu