tca_correct question

[slaterson-2]

should tca_correct be run on every image?  my simple test is telling i
should.

to test this (i can't seem to find docs or a howto anywhere) i took 3
photos from a bracketed set of photos for a pano.  the three photos
are one 'bracket', -2 ev, 0 ev and +2 ev for one camera position.  i
ran tca_correct on them and got three different sets of values to pass
to fulla.

should there be one set of values per lens or per photo?

thanks!




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[Erik Krause]

slaterson <campbell.christopher@...> wrote
> should tca_correct be run on every image?  my simple test is telling i
> should.

I wouldn't do this.

> to test this (i can't seem to find docs or a howto anywhere) i took 3
> photos from a bracketed set of photos for a pano.  the three photos
> are one 'bracket', -2 ev, 0 ev and +2 ev for one camera position.  i
> ran tca_correct on them and got three different sets of values to pass
> to fulla.

This is quite normal. Any automatic approach can not account for effects
that look like TCA but are not. Overexposed areas often cause stronger
fringing f.e.

> should there be one set of values per lens or per photo?

For a given lens (and focusing distance) you should have one set of
correction parameters. Use a sharp image for calibration without
overexposed ares. Use v (FoV) optimization only for the time being.
There are little lenses that show non-linear TCA which would require a,
b or c parameter.

More information on
http://wiki.panotools.org/Tca_correct
http://wiki.panotools.org/CA

--
Erik Krause

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[slaterson-2]

On Oct 29, 4:19 pm, Erik Krause <erik.kra...@...> wrote:

> > should there be one set of values per lens or per photo?
>
> For a given lens (and focusing distance) you should have one set of
> correction parameters. Use a sharp image for calibration without
> overexposed ares. Use v (FoV) optimization only for the time being.
> There are little lenses that show non-linear TCA which would require a,
> b or c parameter.

does any particular photo subject make for better calibration
results?  i.e., black/white lines, color target, etc?

thanks for the info, this helps a lot.
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[Erik Krause]

slaterson <campbell.christopher@...> wrote

> does any particular photo subject make for better calibration
> results?  i.e., black/white lines, color target, etc?

Yes. Since colored structures make it difficult to spot TCA, a less
saturated subject is better. (See
http://wiki.panotools.org/TCA#Difficulties_to_view for details)

A printed target is not recommended if it needs a different focus
distance than your real shots - TCA might change heavily with focus
distance.

I suggest you read the wiki article carefully since it describes how to
determine whether TCA in your images is correctable or not.

--
Erik Krause

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