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. Author manuscript; available in PMC: 2014 Apr 1.
Published in final edited form as: Ultramicroscopy. 2013 Jan 29;133:10.1016/j.ultramic.2013.01.003. doi: 10.1016/j.ultramic.2013.01.003

Figure 1.

Figure 1

Use of azimuthally averaged Fourier amplitude spectra of empty images to rank the performance of different electronic cameras. Individual Lorentzian functions, which are of the form 11+(ss0)2, are fitted to each Fourier amplitude spectrum. Three parameters – an overall scale factor for each experimental amplitude spectrum, an additive constant, and s0, the spatial frequency at which the function is equal 0.5 – are varied to produce a least-squares best fit between the data and the analytical function. (A) The Fourier amplitude spectrum for the TVIPS TemCam F416 camera, obtained when using 120 keV electrons, is used to illustrate the fitting of a single Lorentzian function to the experimental amplitude spectrum. Corresponding figures for other cameras are shown in the Supplemental material. (B) Comparison of Lorentzian curves fitted to amplitude spectra for two types of scintillator-coupled camera and for a silicon-pixel camera. Solid line: TVIPS TemCam F416 camera, 120 keV electrons; dashed line: Gatan UltraScan 4000 camera, 200 keV electrons; dotted line, Gatan K2 camera, 300 keV electrons.