Re: [Debconf-video] Tips and tricks for the speaker camera in UpperTalkRoom
I've edited together Herman's mails:
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: Shutter
speed, f-stop (iris) and gain amount are all shown in the viewfinder.
If they are not, they are on auto! (possible exception: the gain)
a) Turn gain off. Is the picture too dark? The gain is a flip switch on
the left side, next to the white balance switch. It has three positions
(from top to bottom): High, low and off.
b) Open the iris (shiny metal knob) wide open. Still too dark?
c) Increase the shutter speed (default 1/50s) to 1/25s. The shutter is
set with the menu wheel at the back, near the bottom. If the shutter
speed is 1/25s, you'll see "25" in the viewfinder.
d) Set the gain to 9dB, if the above was not enough.
e) Last resort(!): Use 18dB. Only required in pretty dark environments.
You can also use even longer shutter speeds, with flickering and blurry
results. At 1/6s, the camera sees more than your eyes, in full colour!
With just one of the three exposure settings (shutter, iris, gain) set
to auto, manual adjustments will be countered by the automatic control.
This is not what you want. The auto/manual toggle buttons for shutter
speed, iris, gain and white balance are near the bottom on the left
side.
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