High transmission and true color neutrality.
Spectrometers are optical instruments used to measure the properties of light across a spectrum. Wavelength and intensity are detected to determine the percentage of light that a filter transmits or blocks. The data are displayed as line graphs with light transmission % values for each wavelength measured.
A perfectly flat light transmission curve would yield a perfectly color neutral result. While this is technically impossible, the X4 CPL has the flattest transmission curve of any polarizer on the market - guaranteed. This translates into a more color neutral performance without a color cast.
Increased average transmission also leads to better performance. Higher light transmission allows more light to pass through to the sensor, which translates into faster shutter speeds, sharper images and the ability to use a lower ISO when shooting video. The X4 CPL features the highest average light transmission - 47.18% - of any available CPL without sacrificing polarization efficiency.