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

On Mon, Jun 18, 2007 at 12:26:52AM +0200, Herman Robak wrote:
> 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.

Thank you Herman!

Can we get this printed out? (sorry, yes, I am a lame printer-stupid


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