A process for making an optical film includes stretching a polyolefin film in a first direction and stretching the polyolefin film in a second direction different than the first direction forming a biaxially stretched polyolefin film. At least a portion of the stretching of the polyolefin film in the second direction occurs simultaneous with the stretching of the polyolefin film in the first direction. The biaxially stretched polyolefin film has a length and a width and substantially non-absorbing and non-scattering for at least one polarization state of visible light. The biaxially stretched polyolefin film has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an out-of-plane retardance being 50 nm or greater.