by the source. The information limit of current state-of-the-art transmission electron microscopes is well below 1 Å. The TEAM project at Lawrence Berkeley National Laboratory resulted in the first transmission electron microscope to reach an information limit of <0.5 Å in 2009 by the use of a highly stable mechanical and electrical environment, an ultra-bright, monochromated electron source and double-hexapole aberration correctors. Optimum defocus in high resolution transmission electron microscopy Choosing the optimum defocus is crucial to fully exploit the capabilities of an electron microscope in high resolution transmission electron microscopy mode. However, there is no simple answer as to which one is the best. In Gaussian focus one sets the defocus to zero, the sample is in focus. As a consequence contrast in the image plane gets its image components from the minimal area of the sample, the contrast is localized (no blurring and information overlap from other parts of the sample). The contrast transfer function becomes a function that oscillates quickly with Csu4. This means that for certain diffracted beams with a spatial frequency u the contribution to contrast in the recorded image will be reversed, thus making interpretation of the image difficult. Scherzer defocus In Scherzer defocus, one aims to counter the term in u4 with the parabolic term Δfu2 of χ(u). Thus by choosing the right defocus value Δf one flattens χ(u) and creates a wide band where low spatial frequencies u are transferred into image intensity with a similar phase. In 1949, Scherzer found that the optimum defocus depends on microscope properties like the spherical aberration Cs and the accelerating voltage (through λ) in the following way: where the factor 1.2 defines the extended Scherzer defocus. For the CM300 at NCEM, Cs = 0.6mm and an accelerating voltage of 300keV (λ = 1.97 pm) (Wavelength calculation) result in ΔfScherzer = -41.25 nm. The point resolution of a microscope is defined as the spatial frequency ures where the contrast transfer function crosses the abscissa for the first time. At Scherzer defocus this value is maximized: which corresponds to 6.1 nm−1 on the CM300. Contributions with a spatial frequency higher than the point resolution can be filtered out with an appropriate aperture leading to easily interpretable images at the cost of a lot of information lost. Gabor defocus Gabor defocus is used in electron holography where both amplitude and phase of the image wave are recorded. One