https://sphire.mpg.de/wiki/ 2026-05-23T17:50:29+00:00 https://sphire.mpg.de/wiki/ https://sphire.mpg.de/wiki/lib/tpl/dokuwiki/images/favicon.ico text/html 2018-06-20T13:12:12+00:00 Anonymous (anonymous@undisclosed.example.com) https://sphire.mpg.de/wiki/doku.php?id=definitions:absolute_frequency_units&rev=1529493132&do=diff Absolute frequency Definitions Inside SPHIRE, spatial frequencies are handled in absolute units. This means that the spatial frequencies are expressed in term of pixels, or absolute frequency $f_a$, instead of units of inverse distance. The Nyquist frequency, the maximum spatial frequency contained in an image, corresponds to $f_a=0.5$$f_N=\frac{1}{2p}$$p$$f_s$${Å}^{-1}$$f_a$$p$$$ f_s=\frac{f_a}{p} \\ f_a=f_s \times p $$$0 \leq k \leq 0.5n$$$ f_s=\frac{k}{n \times p} \\ f_a=\frac{k}{n} $$$r$$$…