Power Spectrum: intensity [= squared amplitude] of the Fourier transform, presented either in the form of an image (= the outcome of the PW operation) or as a profile (= the outcome of averaging the 2D power spectrum azimuthally). [Note that the SPIDER operation PW furnishes the amplitude, not the squared amplitude! This makes it easier to use the distribution in displays and other operations, because of the high dynamic range]. The complete length of the abscissa in such a plot corresponds to the highest resolution represented in the digitization: 1/(2 x sampling distance). For example, if the scanning is done with 20 microns, and the electron optical magnification was 50,000 x, then the highest resolution represented in the digitized image is 5 x 10**4/(2 x 20 x 10**4) A**(-1) = 1/8 A**(-1). This means that the total length of the abscissa corresponds to 1/8 A**(-1) in this case.

 

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