Talk:Dust Removal with Flatfield

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Revision as of 21:09, 2 December 2007 by Klaus (Talk | contribs)

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Starting the writing

Some text I have recycled from a web page I wrote a few months ago.

Also some of the images can be found in higher resolution on commons.wikimedia.org and I wonder whether I should upload them here in full resolution as well when the size is in the 7-8MB range.

Regarding the flatfield implementation in hugin0.6, choosing division there, is it converting full black into 0 and full white (0xff in an 8bit greyscale TIFF) into 1 and then division? This I would prefer.

Or is it

  -f filename      Vignetting correction by flatfield division
                   I = I / c,    c = flatfield / mean(flatfield)

with normalising to the flatfield average like it is described for Fulla? In the case of dust speck correction this would be inconvenient as away from the dust spots the correction should be transparent with a division by exactly one.

How does one create a greyscale TIFF file with 16bit depth?

With 8bit depth I see the necessity of manually dithering the flatfield in order to avoid posterisation. Previous steps in generating the flatfield rely on large radius Gaussian blur which means that high frequency image noise that otherwise would do some "dithering" mostly disappears.

Maybe someone can teach me how to get 16bit with gimp ;-) -- Klaus 20:09, 2 December 2007 (CET)

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