On Tue, 2011-07-26 at 22:59 +0100, Stefano Rovetta wrote:
> > I can do the lens correction with ufraw manually, but there
> > are three
> > parameters, and it is hard to figure out how to adjust them
> > visually.
> After a very quick googling I landed here:
> As far as I can understand, this is the model used by UFRaw.
> You might calibrate the parameters for each of your lenses with the aid
> of the model and some reference image (e.g. you can print a grid
> on paper and take a photo with your lenses, setting the zooms at
> significant positions like max wide/max tele/center).
> Then you can guess the parameters by analyzing the correction formula,
> or you can even write a distortion measure and minimize it analytically
> - I am sure you have the necessary background to do that, and it can
> even be fun to do it.
Actually, I am familiar with the lens model, and at one point I tried to
calculate the coefficients for a lens I had. It is not conceptually
difficult, but it is harder in practice to do than one might imagine. I
would rather not do it if it has already been done. As I remarked, the
gimplensfun filter does a very good job based on what it finds in the
exif file, and it works very well for my 18-200 mm Nikkor lens. So
ufraw should be able to do as well. I think it is bug in ufraw and I
hope someone will fix it soon.
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Leonard Evens l...@math.northwestern.edu
Professor Emeritus, Department of Mathematics, Northwestern University
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