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
Medical Scientist Training Program
Dallos Laboratory
F. Searle 1-240
2240 Campus Drive
Evanston IL 60208
lab: 847.491.2438
cel: 773.608.9185
email: j-kell...@northwestern.edu
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