If complacency is not the friend of business, then digital technology must be its bane. Exhibitors are pitched upgrades that deliver higher frame rates, higher luminance, wide color gamut, and immersive sound, little of which provides a clear path to monetization. Rather than shell new capabilities out in bits and pieces, one might think it better to bottle them up and ship all at once. If such an ideal were to be possible, what would this next gen cinema consist of?
The surprising answer would be nothing that’s available today. With all of the talk of laser illuminators, 4K resolution and high frame rate projectors, what cinematographers want to see requires improvement in other areas, including higher dynamic range, significantly improved contrast, and higher bit rate images.
High dynamic range (HDR) in cinemas is only now being explored, and the technology that will drive affordable projectors in this area has yet to emerge. There are two components of HDR to be considered: the peak image brightness useful for telling stories, and the practical image contrast that can be experienced in an auditorium. Dolby Cinema has settled on peak image brightness that is twice that of standard dynamic range cinema, for example. There is some convenience to this number in that it is difficult to go beyond it with even the best of current projection technology. From a recent round of papers given this month at the SMPTE conference in Los Angeles by RealD and Barco, the average image brightness of real movies is in the range of 5-7% of standard peak luminance (48 nits or 14 ft-L). If the ratio of average to peak in standard cinema is in the 10 to 20 range, then will a ratio of 20 to 40 provide significant improvement in value to the audience? If not, where is the sweet spot? This is an area where there is more to learn.
Image contrast is affected by both environmental and performance factors. DLP Cinema projectors are touted to deliver 2000:1 sequential contrast ratio, but actual measurements of sequential contrast in a cinema will deliver lower numbers. In his SMPTE paper, Miller Schuck, Chief Scientist of Optical Systems at RealD, defines system contrast as a function of that of the projector, the room, and veiling contrast introduced by system optics. His research indicates that system contrast in cinemas has a ceiling of 10,000:1 to 20,000:1, after which further improvement in contributing factors cease to improve the final result. This is an important step towards determining design goals in next generation projectors. It’s also useful in understanding current high-end projectors, namely those from Dolby and IMAX. Dolby claims contrast of 1,000,000:1, while IMAX claims contrast up to 8000:1. Perhaps the difference isn’t as great as it sounds. Technologies that bring high contrast to market at affordable prices have yet to emerge.
Compression bit rate may well be the least appreciated factor in image quality. Compression bit rate is inversely proportional to the compression rate applied to the image. Present day media blocks are limited to 500-700 Mbps, which is more than the 250 Mbps required of DCI, but not enough for preserving quality in 4K 3D and high frame rate images. A definitive study towards determining a new bit rate ceiling for next gen content has yet to take place. However, interest in this area is stirring, and evaluation testing could take place 1st or 2nd quarter next year.
Missing from this discussion is wide color gamut (WCG). WCG is an important topic in home entertainment, where the HD Rec 709 standard defines a smaller color gamut than the DCI P3 minimum required of digital cinema, and an improvement is needed. The new standard for home entertainment, Rec 2020, defines a container color gamut that is larger than DCI P3 minimum, but still smaller than the XYZ container defined for digital cinema. In addition, DCI P3 is quite good, and not expected to be demonstrably insufficient when compared to Rec 2020. While study in this area will be useful, it is expected that the factors outlined above will deliver higher value to audiences.
News that next gen cinema has more work to take place before entering the market may not be what cinematographers want to hear. After all, next gen motion picture cameras are now on the market that can deliver all of the above today. The fact that source material can now be delivered with characteristics that go beyond today’s cinema is fuel for engaging in studies that determine a new set of performance targets.
It’s tricky business, however, to establish a new set of performance targets. Who will be the voice? If it’s DCI, then the targets will be associated with Hollywood studios, which have no intention to fund a transition to next gen cinema technology. The purpose of setting new targets is to educate the exhibitor as to what to buy, and to provide meaningful parameters to filmmakers who like to push limits. If the emergence of next gen features takes place organically and somewhat chaotically, then the burden will be on distribution to fulfill the chaotic requests, an inefficient undertaking. Better to provide some structure to this. May the testing begin.