Optimal cell retardation value at which the maximum transmittance occur in a fringe-field switching (FFS) mode is analyzed theoretically and experimentally. In the device, the rotation angle of liquid crystal (LC) director is dependent on electrode position. Nevertheless, the transmittance can be described using a uniaxial medium model within a certain cell retardation value like in the in-plane switching (IPS) mode, where the effective birefringence was reduced to about 76% of the original value.