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Illustration of missing wedge in 2D, using a model sarcomere

a                                         b                                   c                                 d                                        e    

(a) Schematic muscle sarcomere with Fourier transform in the inset above. 

(b) High-pass filtered resulting from the Fourier transform filtered with the mask above.

(c) Low-pass filtered.  This results in blurring fine detail.

(d) Wedge-filtered, illustrating the case in the electron microscope with the tilt axis along the sarcomere axis.  Filaments are clearly resolved but perpendicular elements (M-line) are suppressed.

(e) Wedge-filtered, tilt axis now perpendicular to the sarcomere axis.  Now all filaments are suppressed but M-line is clearly resolved.

For this example, dual-axis tilt-series as commonly used in electron tomography is homologous to combining both the wedge-filters, hence the original image would be obtained.