Ins and outs of digital electron microscopy.

In order to do any sort of computer processing of the images produced by an electron microscope they have to be digitized. Therefore, any form of microscopy that involves computer processing has to be considered as digital microscopy independently of whether the original images were recorded on film and scanned or recorded directly on a digital medium such as the charge coupled device (CCD). As soon as one digitizes images, one encounters a range of effects and artefacts specific to the digital world such as aliasing, quantization errors, and ambiguities in the modulation transfer function. Even a quick discussion of these effects makes it clear that what comes out of a digitizer is not related in a simple way to what goes in. After introducing the commonly used recording media, I will discuss the most important effects of digitization and then compare the limitations and advantages of the different recording media for various applications.