We first focus on the role of the instrumental resolution in Elastic Incoherent Neutron Scattering (EINS) where the connection between the Self Distribution Function (SDF) and the measured EINS intensity profile is highlighted. Second we show how the SDF procedure allows both the total and the partial Mean Square Displacement (MSD) evaluation, through the total and the partial SDFs. Finally, we compare the SDF and the Gaussian procedures, by applying the two approaches to EINS data collected, by the IN13 backscattering spectrometer (ILL, Grenoble), on aqueous mixtures of two homologous disaccharides, i.e. sucrose and trehalose, and on myoglobin.