[en] Highlights: • Trans-RPSB S₀ and S₁ PESs, MECIs and MEPs connecting the FC point studied with SI-SA-REKS. • QTAIM explained the consequences of the variation in the bond length alternation distortion. • The ellipticity ε variations explained by the range of existence particular closed-shell BCPs. • Quantum topology phase diagrams quantified the clockwise and counter-clockwise torsions. • Explained why the order of favorable torsion θ was C7C8 BCP > C9C10 BCP > C11C12 BCP. A QTAIM investigation of the torsion in both the clockwise and counter-clockwise directions about the π bonds of the retinal protonated Schiff base chromophore in the lowest electronically excited state provided a detailed description of the changing bonding topology that was sensitive to both the torsion and the direction of torsion. Analysis of the separate torsion calculations demonstrated a clear order of preferred bonding torsion in terms of principles of maximizing bonding. Unusual behavior of the bond ellipticity in the S₁ state was found for the two less favorable bonds for torsion and explained in terms of the presence of weak bonding interactions.