10685Re: [PanoToolsNG] Re: Chromatic Aberration on fisheye lenses images (comparative test)
- Jul 2, 2007http://tinyurl.com/2zzjsl
Based on other experiment that you may replicate, I have proposed
some additional conjectures on the same subject.
Le 1 juil. 07 à 20:03, Rik Littlefield a écrit :
> --- In PanoToolsNG@yahoogroups.com, "Serge Maandag (yahoo)"[Non-text portions of this message have been removed]
> <yahoo@...> wrote:
> > > Six different fisheye lenses have been subjected
> > > to a comparative test in order to assess
> > > their respective propensity to TCA.
> > > The influence of light illumination spectrum
> > > on TCA has also been studied.
> > >
> > > You may read the report here:
> > > http://tinyurl.com/32jjdz
> > That's a weird result...
> > You would expect the blue abberation to be more pronounced
> > under light that simply contains a bigger part of the
> > blue spectrum. But not that the light source would
> > change the scaling of the abberation.
> The thing to remember is that the aberration depends on wavelength,
> not just on "red" versus "green" versus "blue".
> Two different wavelengths may both record only in the "blue" channel,
> but nonetheless be shifted by different amounts.
> What gets recorded in the "blue" channel is a kind of weighted
> average of the shifts over all of the different "blue" wavelengths
> that were present in the illumination.
> If the different light sources have different proportions of various
> wavelengths in the "blue" band, then those sources will show
> different TCA.
> In summary, it is the detailed shape of the spectrum -- where are the
> peaks and valleys? -- that cause TCA to be different for different
> light sources.
> The phenomenon called "metamerism" is due to a similar cause. Much
> info about that can be found by googling. A good place to start is
> to Google "define: metamerism" and to read
> http://en.wikipedia.org/wiki/Metamerism_(color) .
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