To verify the performance of ESR films represents a measurement challenge for many commercial spectrophotometer systems. Not only are ESR films designed to achieve very high reflectance (>98% R) in the visible spectral range, but are required to achieve this high reflectance at any angle of incidence and under any state of light polarization. Therefore, the ESR films need to be measured with an absolute variable angle reflectance accessory combined with an automated polarization accessory.