Pete Lude from Mission Rock Digital gave a presentation on the state of LED cinema screens at the HPA Tech Retreat that was similar to one he gave at IFA last September, but with updates, of course. For example, he says there are now 10 installed LED screens in cinemas and LA could see the first LED screen installed in the US by April (2K for post production, as we reported from ISE).
His presentation provided a very nice overview of the reasons why LED screens offer such a compelling option for cinemas including deep black levels, higher luminance, HDR capabilities, bright 3D presentations, screen format flexibility, the ability to offer lights-on entertainment, power savings, operational benefits and more.
The trends for LEDs are clearly favorable, he noted, with the chart below showing how LED efficiency (Haitz’s Law) and cost have progressed incredibly.
New LED technologies like Chip On Board and microLED will be very helpful in realizing LED solutions for cinema screens, but cost remains the major issue today. He showed some data from FutureSource Consulting that showed the cost reductions for several 3-in-1 LED SMD packages (0.8, 1 and 2mm square). This suggests a cost reduction of 55% to 75% over the last two years with this trend expected to continue
Using SMD LEDs today for a 4K cinema screen means the LEDs would cost perhaps $0.05 per full color pixel, with the total system running up to around $0.08/pixel, or $700K. This compares to an RGB laser projector with 4K resolution costing in range of $200K to $300K, or 3 to 4 cents per pixel.
The other cost of the LED display, like the drivers, circuit boards, cabinet materials are not expected to be reduced that much over time, so cost savings need to come from the LEDs. Getting their cost down to around $0.02 per full color pixel is needed to drive main stream adoption, he thinks. But, this could be just 2-3 years away.
Clearly, Chip on Board (COB) and microLED technologies could be the answer to driving costs even lower, said Lude. COB is already used in lighting fixtures and five manufacturers have started to introduce COB for displays (see our report on this from ISE (Absen Develops CoB LED Technology). The reduced packaging costs vs. SMD and better thermal management and ruggedness, wider viewing angles plus the ability to get higher density and/or smaller LED devices are very attractive for COB, but it is still early days (as was noted at ISE, contrast is still lower in COB).
microLEDs would allow the LED size to shrink even further – with each LED perhaps being surrounded by black as with the Sony CLED display, to improve contrast. Pixel pitches do not need to be that aggressive for a cinema display. Samsung’s CinemaScreen has a 2.5mm pitch – hardly state of the art. (but almost certainly the lowest cost per pixel at the moment – Man. Ed.)
Lude then laid out the major issues that confront being able to transition from projection-based cinemas to LED-based screens. This includes:
- Screen size and scaling
- Image quality
- Sound
- System integration
- Stereo 3D
- Cost
Screen size is driven by the pixel pitch, which we already have noted, does not have to be that fine because theaters viewing distances are large. But if some theaters want a 40’ screen with a specific pitch, the resolution of the screen may not be a standard DCI 2K or 4K. That means scaling will be needed, which is not currently permitted for cinema content. Should this be revisited for LED cinemas, Lude wondered?
Image quality covers a number of parameters including color gamut, linearity, contrast, off-axis uniformity, seaming and temporal artifacts. No specifications for these parameters exists, not to mention agreed upon metrology for measuring it. Remember, these can be HDR displays and Hollywood is very insistent upon having a controlled image in the theaters.
Most LED screens are not transparent so mounting speakers above or to the sides must be considered. But how can you control the sound so voices appear to come from the characters mouths on-screen? In addition, we are now seeing some transparent LED screens emerge which could allow speakers to be placed behind the screen, as they are now.
System integration goes beyond assembly and eliminating any visible seams. It also means security so it is impossible to “tap” into the signal and steal the content. DCI governs this in today’s theatrical world and will continue to guide this in the future, but will modifications be necessary in the era of LED screens? (see comments about this from Samsung at ISE (Samsung Really Emphasises LED) – Man. Ed.
Stereo 3D is still very popular in much of the world and one of the big benefits of LED screens is their ability to deliver a high brightness 3D image. But what is the best solution: passive or active glasses? Each has their trade-offs, noted Lude (and as we learned at ISE, Hollywood is not very supportive of the active approach, which Samsung demonstrated at ISE).
In conclusion, Lude finds that there are technical challenges to developing LED-based cinema solution but they are solvable problems. The most important challenge is cost, but he is optimistic that in a few years, mainstream cinemas will be ready to consider adopting the technology. – CC
