color correction & vignetting [Re: [ptx] Hugin wishlist, RFC]

[Pablo d'Angelo]

On Wed, 04 Feb 2004, Pablo d'Angelo wrote:

> Before we start with exposure compensation we have to tackle another lens
> defect, namely vignetting. I found that my camera produces gray level
> differences of ~ 40, if zoomed out.
> 
> The pano tools plugins have a simple p = b*r^2 * p  (where p=pixel value)

Ehm, sorry, pano tools uses additive instead of multiplicative correction
 a*R^2+b  (b=brighness), a=coefficent. See also:
http://www.email-lists.org/pipermail/ptx/2003-October/000721.html

I'm not sure if we should go with a formula (simple for the user), or if we
should use a flatfield, like it's done in astronomy. Comments welcome.

I think the flatfield is harder to create. on the other hand, maybe its
feasible to fit the parameters for the correcting, radial function if images
with high overlap and without scene changes are used.

ciao
  Pablo
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