3D systems for movies using polarized light cause a loss of screen brightness due to the inherent filter absorption. The polarization filter in front of the projector blocks half of the projecting light, reducing screen brightness. However, as half of all other ambient and reflected light in the theater is also reduced by the viewing lenses, the perceived contrast does not suffer excessively. The overall effect is that of wearing a pair of slightly darkened glasses in a standard movie theater, which could be compensated by using brighter projector lamps.
One complaint with many 3D display systems is that some viewers may feel nauseated or experience a headache. This effect is more likely with rapid cuts between scenes with very different depth, which directors and editors of 3D movies generally try to avoid.