PanoTools:
Re: Re: My attempt to eliminate vignetting effect
Glenn Barry 2004-Nov-30 22:36:43
What about if people are prepared to do a flat field calibration of
their lenses at various apertures, saving those in somethng like an 8 or
16 bit greyscale mask for future reference.
Which wouldn't be much different to calibrating the distortion
co-effients as people do currently.
Then as you mention loading those masks for stitching transformations,
even if they are loaded separately, and saved out with correspondng file
names for application later.
Sorry if this has already been mentioned, I'm catching upo on old mail.
Glenn
Pablo d'Angelo wrote:
> Hi Erik,
>
> Erik Krause wrote:
>
>
>>>The big technical hurdle will be that currently enblend knows nothing
>>>about the original, pre-transformation image coordinate system.
>>
>>[...]
>>
>>
>>>Thoughts?
>>
>>I fully agree. May be it is not needed for enblend to know the
>>orignial coordinate system. Panotools could either provide another
>>channel with a mask (similar to the levels mask Valeriy uses)
>>indicating the amount of correction. This mask could undergo the same
>>transformation as the original image. (I think nona had a feature
>>like this).
>
>
> Yes this was an early version of nona that used the radial distance
> during the stitching and wrote it into temporary tiff files that didn't
> get deleted after the stitching ;)
>
> I might readded the creation of these tiff files if there is interest
> for deveopers. While I think the whole idea is good, unfortunately I
> don't have the time to implement the full algorithm.
>
>
>>Or better: In a separate TIFF tag there could be some data that
>>allows enblend to calculate the displacement by itself.
>
>
> Of cause this would be a better thing, because it can be calculated on
> the fly, without the need for big distance map images.
>
> I have used the flatfield technique to estimate vignetting and similar
> darkening effects of my camara (Canon A40 ;) some time ago, and I found
> that it was not completly radial, and quite out of the image center. So
> the radial correction wouldn't be perfect, but I guess it should be
> better than nothing.
> Maybe the vignetting center could be optimized during the correction as
> well.
>
> ciao
> Pablo
>
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>
>
>
> Yahoo! Groups Links
>
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