We revisit the techniques we have developed for the characterization of the optical system of the soft X-ray Mistral microscope to obtain resolution, depth of field and degree of coherence and how they are used to apply the XTEND framework to computationally extend the depth of field in tomographic reconstructions based on focal series projections. Furthermore, we analyse the current limitations of these methods and introduce new proposals about how they could be improved. Finally, I present my current developments in the optimization of the computational process for cryo electron subtomogram averaging technique, specially tailored to Relion package.