Gary Feather of Nanolumens spoke next and provided an overview of the wide performance capabilities of LED direct view displays along with their diverse use in terms of applications. He explained that LED screens are passively driven using pulse width modulation (PWM) and a multiplexing screen. Typical LED drivers are 1/32 or 1/16 multiplexed.To achieve 700 cd/m² for example, several standard RGB SMT packages are available for these drivers. But if the multiplexing was lower at 8 or 4:1, then a much smaller LED could be used. Any LED saving would have to be weighed against an increase in driver chips, however.
For cinema, he argued, you want to keep the mid tones of the content in about the same range it is today even for HDR cinema as this is the right level for dark room adaption. That means the LEDs only need to really produce 50-100 cd/m² – a very low level for LED technology that can be accomplished with much smaller LEDs. HDR can be used for specular highlights. But he argued, these highlights can be accomplished by adding a white LED to the mix that kicks in above perhaps the 50-100 cd/m² level provided by the RGB LED. Peak (white) specular brightness up to 4,000 cd/m² is possible, said Feather. This combination of much smaller LEDs, lower multiplexing, an RGBW architecture plus sub-pixel rendering could offer a much more cost effective solution for LED cinemas, he postulated. How filmmakers would react to such an approach is a big unknown, however.
Feather also noted in response to a question that Nanolumens can do stereoscopic 3D by adding a circularly polarized checkerboard film to the display, but that does mean a loss of resolution and luminance. With their proposed solution, Feather thinks the HDR cinema era can begin now, but it will take 20 years to replace the majority of projectors. – CC
