Electric field modulated spectra of polymer films are compared with those of single crystals to study the influence of disorder on size and shape of the effects. The quadratic Stark effect is similar as in crystals but reveals even in isotropic films pronounced anisotropy. Disordered films show an additional response quadratic with the field but of second derivative line shape which is interpreted as linear Stark effect due to dipole moments induced by asymmetric boundaries of chain segments.