Selected photometric bands, spatial resolution, disk dimension in the frame and the scanned sky background level are determined in order to establish galactic structural parameters. A crude analysis could lead to erroneous results. Possible causes of error, as well as the minimum requirements for a precise determination of parameters, will be discussed. Our main goal is to separate morphologically the dynamical components of galaxies in order to model their 3D structure and to estimate their gravitational potential. Also important is to study their stellar populations and histories. A population analysis of the different structures of the galactic components with OSIRIS tunable filters on the GTC is proposed.