Re: advice needed on camera raw data image filtering...
From: Martin Leese (please_at_see.Web.for.e-mail.INVALID)
Date: 11/03/04
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Date: Tue, 02 Nov 2004 20:40:02 -0700 To: lucy <losemind@yahoo.com>
lucy wrote:
> Hi all,
>
> We used camera to do some imaging and got some raw image data, which are
> very noisy at the low signal end(where there should be some low signal) or
> the dark end(where there should be no signal theoratically)... we have
> learned from Jerry and others in DSP group that we should
> take a picture of completely dark NULL object and then do a subtraction:
>
> picture with meaningful object images - picture with NULL object =
> noise-reduced image...
This looks like an attempt to correct for uneven
illumination. It will not produce a noise-reduced
image.
> Then what do we do after that? Use what filter to reduce noise?
Image acquisition is everything. Go back and
re-take the images. If you suffer from noise in
the dark areas then illuminate them so that they
are less dark. Also, adjust the illumination to
make sure you are using the full range of the
camera. As a rule of thumb, you should be
taking two to three hours to set up the
illumination.
Then, if you still have problems with noise,
use ensemble averaging; there is no better way
to reduce noise.
-- Regards, Martin Leese E-mail: please@see.Web.for.e-mail.INVALID Web: http://members.tripod.com/martin_leese/
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