1. Method for correcting distortion errors in a 3D content viewed by an observer on a screen; the method being wherein it comprises the step of determining a rendered roundness factor (rrf) for the observer of the 3D content depending of the defined distance of the observer to the screen and of the disparity; determining for the observer a disparity transform function (TD) as a function of the determined rendered roundness factor so that the disparity values of objects of the 3D content are corrected for obtaining a perceived roundness factor of one.