[CREATE] Lens correction database

[Andrew Zabolotny]

From Thu, 10 Jan 2008 14:01:35 +0100
Pablo dAngelo <Pablo.dAngelo at web.de> wrote:

> Actually, my suggestion would be to just ignore this issue,
That's what I'm going to do so far :) But the approach with calibration
focal distance deviation with distance-to-subject can be added later
without invalidating any of the data previously collected.

> Hmm, does the vignetting really change noticeably with
> varying focus? I haven't made any analysis in that direction
> yet.
It does, and for example for my Pentax 18-55mm it is very noticeable.
Perhaps that's due to mechanical vignetting, optical vignetting
shouldn't change that much imho.

> The Zhang algorithm, for example as implemented in Bouguet's 
> matlab toolbox or the CamChecker program are suitable for this,
> and will likely provide higher quality estimates as a 360°deg
> panorama.
Zhang distortion model seems pretty simplistic to me... as far as I
understand it was targeted at webcams (e.g. pinhole lenses). I
haven't even included it in lensfun so far, but it's easy to add
it as soon as somebody needs it. Besides, it does not evaluate chromatic
aberrations and vignetting. Calibrating TCA should give a good
increase in image sharpness towards the edges... and this would be
pretty neat for panoramas, especially if you don't overlap the images
too much.

> > For vignetting we have PTLens anyway ;-)
> PTLens is not open source and when I last looked,
> PTLens only offered an interactive vignetting correction.
Sorry, it's my error - I was meaning Hugin. In most of my experiments
it computed vignetting parameters quite well.

> Btw. how is progress on the ufraw integration?
I've finished the draft UI and now I'm implementing a system where
arbitrary filters can be inserted into the de-bayering chain. I'd say,
50% complete.

-- 
Andrew
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