Camera saturation - image compression level

Sascha Silbe sascha-ml-ui-sugar-olpc-devel at
Thu Dec 3 08:34:04 EST 2009

On Thu, Dec 03, 2009 at 11:32:37AM +0100, Bastien wrote:

> some people in France (from La main à la pâte) designed a telescope 
> for
> the XO.  It's a cheap ad hoc device they stick close to the camera, 
> and
> it can zoom by 10x -- useful for observing, say, the moon.

> - is there a way to take pictures with a higher resolution?  the  
> default compression level doesn't produce great pictures.
Others will probably have better ideas, but maybe I can get you started.
I don't think you'll be able to do really nice shots with the built-in 
camera as it's a simple, low-res webcam. To check whether Record causes 
any additional degradation, try to use some command-line V4L tool, e.g.:

vgrabbj -o png -d /dev/video0 -i vga -S -f x.png

For your saturation problem, you might try whether "-a" (maybe combined 
with "-F 4" and/or "-z <number>") have any effect; also try using daemon 
mode to capture multiple images and throw away the first one as that 
worked better for me than -z. v4l-info and v4l-conf (both from v4l-conf) 
might be useful as well.

If the XO-1 and your add-on are sufficiently steady, you might try doing 
several shots and combining them using some filtering technique to 
increase the resolution (i.e. color depth, not image size - the image 
position isn't varied between shots); there's certainly enough noise for 
this to work. ;)

CU Sascha

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