Hello,
I was recently advised to have a look at James Holton's videos
to have an idea of the effects of various parameters.
http://ucxray.berkeley.edu/~jamesh/movies/
There is a video "The importance of Phase":
http://ucxray.berkeley.edu/~jamesh/movies/dephase.mpeg
This is not an explanation, but a very nice illustration
I think.
This page has examples in image processing:
http://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm
The "Guidelines for Use" section shows an image,
and what you get if you do an inverse FFT while
ignoring the phases.
Regards,
Francois.
Jacob Keller wrote:
> Dear Crystallographers,
>
> I have seen many demonstrations of the primacy of phase information for
> determining the outcome of fourier syntheses, but have not been able to
> understand intuitively why this is so. Amplitudes as numbers presumably
> carry at least as much information as phases, or perhaps even more, as
> phases are limited to 360deg, whereas amplitudes can be anything. Does
> anybody have a good way to understand this?
>
> One possible answer is "it is the nature of the Fourier Synthesis to
> emphasize phases." (Which is a pretty unsatisfying answer). But, could
> there be an alternative summation which emphasizes amplitudes? If so,
> that might be handy in our field, where we measure amplitudes...
>
> Regards,
>
> Jacob Keller
>
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> Jacob Pearson Keller
> Northwestern University
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