A method for manufacturing a film or sheet comprises deforming a polymeric alloy at a temperature effective to impart to the deformed alloy a birefringence retardation of greater than or equal to about 750 nanometers. A method eliminating comets and veins in an optical film or sheet comprises annealing the film or sheet to a temperature greater than the lowest glass transition temperature of the polymeric resins contained in the alloy. A composition comprises a first polymeric resin in an amount of about 1 to about 99 wt %; and a second polymeric resin in an amount of about 1 to about 99 wt %, wherein the polymeric resins are blended with a deforming force effective to produce a polymeric alloy having a birefringence retardation of greater than or equal to about 750 nanometers.