At least one exemplary embodiment is directed to an optical system which includes a plurality of refractive optical elements arranged substantially symmetrically with respect to an aperture-stop. Furthermore the optical system comprises a refractive optical element being constituted by a solid material. An Abbe number .nu.d of the solid material and a partial dispersion ratio .theta.gF of the solid material can satisfy the following conditions: .theta.gF-(-1.665.times.10.sup.-7.nu.d.sup.3+5.213.times.10.sup.-5.nu.d.s- up.2-5.656.times.10.sup.-3.nu.d+0.755)>0, .theta.gF-(-1.665.times.10.sup.-7.nu.d.sup.3+5.213.times.10.sup.-5.nu.d.s- up.2-5.656.times.10.sup.-3.nu.d+1.011)<0.