It is well known that 3D systems are very inefficient and lose up to 85% of the available light compared with the same projection system operating in 2D mode. High gain screens can be very useful to boost light levels. Polarised light 3D systems use "silver" screens, which have an intrinsically high gain (typically 2.4). 3D systems using other technologies use "white" screens. Previously, the highest gain available from Harkness was 1.8 (Perlux 180). Now the company have developed Perlux 220 with a peak gain of 2.2 specifically for 3D systems. This enables higher brightness levels on larger screens when showing 3D, with an acceptable viewing angle in 2D mode, which is useful when there is mixed programming. The half-gain angle is 25°.
The Perlux 220 screen is also suitable for very large 2D screens where the highest possible gain is required and screens up to 26.5m wide (87ft) are available. Perlux 220 has been used already in conjunction with Dolby 3D systems in several locations.