In this paper, we discuss various technical options to implement 3D dual-view systems, from four frames generated by two triggered or non-triggered 3D projectors. Such a technique offers 3D free-viewpoint capabilities for two viewers. We compare two different technical implementations based on transmissive video projection and reflective silver screen, combining two different 3D encoding techniques: polarization and time multiplexing. The main objective is to analyze and mitigate the ghosting effects, as a function of the technical, modal and frame pairing choices with respect, first to the image optical quality and second to prevent visual fatigue. We suggest some solutions to reduce the impact of the physical ghosting and frame unbalance. These solutions will be expanded in a second paper.