1. A method for correcting distortion errors in a 3D content viewed by an observer on a screen comprising: determining a rendered roundness factor for the observer of the 3D content depending of a defined distance of the observer to the screen and of the disparity associated with said 3D content; and determining for the observer a disparity transform function being defined as a function of the determined rendered roundness factor, the function taking into account said defined distance, whatever a value of the defined distance is, so that the disparity values of all objects of the 3D content are corrected for obtaining a perceived roundness factor of one.