[Debconf-video] Tips and tricks for the speaker camera in UpperTalkRoom

["Herman Robak" <herman@skolelinux.no>]

As I looked at one of the freshly encoded high-resolution videos
(079_Free_software_in_the_commercial_environment.ogg)
I noticed two problems: 1) Over-exposure and 2) noise.

1) Over-exposure is best checked with the zebra pattern, which
is turned on with a switch on the back of the camera, near the
top.
 When the zebra function is on, areas which are nearly white
will appear with a flickering zebra pattern in the viewfinder.
If a large part of the speaker's face is covered by the zebra
pattern, gain should be switched down/off, and the iris adjusted,
as needed.
 A quick and dirty way to adjust the image is to turn the iris
down (metal knob on the front) until the zebra disappears, then
turn it gently up until a few areas become "zebraed".  Things that
are supposed to look bright white should be zebra-patterned.

2) If the final encoded video has visible noise, gain must have
been used.  The "low" dB setting gives only very subtle noise,
which the encoder may suppress completely.  If the noise is
obvious, 18dB gain ("high") was probably used.
 Instead of gain, open the iris (lowest number/largest opening
is f:1.6) or use 1/25s shutter speed:
a) Turn gain off.  Is the picture too dark?
b) Open the iris (shiny metal knob) wide open.  Still too dark?
c) Increase the shutter speed (default 1/50s) to 1/25s.
d) Set the gain to 9dB, if the above was not enough.
e) Last resort(!): Use 18dB.  Only required in pretty dark environments.

--
Herman Robak