This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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In most HRTEM measurements one usually uses an objective aperture that cuts off all distances smaller than the point resolution, making the atom columns appear as single black spots which makes the images interpretable, but means that a lot of information about the sample is lost.

For analytical HRTEM imaging, a sufficiently large objective aperture is normally used such that no loss of imaging information originates from the aperture and the effect of circular function, A(k), can be ignored.