PURPOSE: To obtain a photosensitive composition exhibiting photoresponsiveness of sufficient magnitude and rate with as low an optical power as possible by incorporating a triarylmethane-base pigment as the pigment. CONSTITUTION: This photoresponsive composition responds to a light of specified wavelength and reversibly changes the transmittance and/or refractive index of the light of different wavelength, and a triarylmethane-base pigment shown by (ϕ<1> ϕ<2> ϕ<3> C)<+> X<-> is incorporated as a pigment. In the formula, ϕ<1> to ϕ<3> are a uni- or bivalent aromatic hydrocarbon or aromatic heterocyclic ring residue linked to the central carbon atom with a carbon atom, and the respective residues are capable of having a substituent, X<-> is a counter anion chemically inert to triarylmethyl cation, where the chemical inertness means that the counter anion does not react chemically with the triarylmethyl cation and interacts electrostatically with the triarylmethyl cation as a mere ion species.
PHOTORESPONSIVE COMPOSITION CONTAINING TRIARYLMETHANE-BASE PIGMENT, OPTICAL ELEMENT USING THE COMPOSITION AND OPTICAL CONTROL METHOD