Each year, I am pleased to be able to shed some light (pun intended) on my favorite display medium, projectors. This year in particular, there is more diversity to talk about than usual. Of course we need to look at the “bleeding edge” of projector technologies such as resolution and solid state illumination, but there are two topics that bear even more examination. I am speaking about high frame rate (or HFR) and a topic that is on everyone’s mind: high dynamic range (aka HDR) and UHD. To say the least, there is a lot going on.
Let’s start our plunge into projection on the hardware side of things. As we all remember, in the not too distant past we migrated up to 1920 x 1080 resolution and that was the beginning of the 16:9 high resolution era. We wanted more detail on screen and we got it, but consumers and AV types alike are never content with the status quo. Digital cinema adopted the initial higher resolution 2K format, and that has lasted for a while… but we all know that the only constant is change. This leads to our current stage of resolution development, 4K. To clear up any confusion, 4K in cinema is 4096×2160 and 4K or more correctly, 4K UHD in consumer and commercial displays is 3,840 x 2160. There are arguments on the relevance of 4K for smaller screen sizes, but in fact, there is more detail, better contrast, more color saturation etc. At any rate, you get the picture. For those who might think we are stopping there, oh no, not the case. NHK (in concert with JVC) over in Japan has been showing prototypes of an 8K projection system. To show that this stage of the resolution evolution is not just an interesting technology demo, the folks at Sharp are currently showing off an 8K flat panel, and Canon is now showing an 8K camera. Once the proverbial cat is out of the bag, technologically speaking, it is only a matter of time till we see more and more proof of concept products followed by the real deal that you can actually buy. This all begs the question as to whether we “need” 8K or not… but that is another article that I am sure will be written in the not too distant future. Let the discussions begin.
Now we turn our attention to a hot topic, projection light sources. We are on the cusp of a new day in illumination. Traditional lamps still rule the roost, but solid state technologies are gaining ground rapidly. A traditional lamp has always had an Achilles heel or two. They may last from as little as 2,000 hours, up to 4,000 hours in an “eco-mode”, and as they operate they decay over time. This means that in the end, they must be replaced, costing time, money, and inconvenience. To address this problem, solid state illumination provides up to 20,000 hours of life. In addition, they do not noticeably decay over that lifetime. If you think about it, the commercial buyer uses their projector an average of 33 hours per month so 20,000 hours is over 50 years, and even in education where the projector is constantly on, it will last 23 years. The projector will be passé before the illumination system fails.
The newest trends in solid state illumination are the hybrid light engines. At the lower end of the light output spectrum, topping out at about 4000 lumens are the companies like Casio, which use a combination of LEDs, a single color laser, and phosphors to produce light. The next group is divided into two categories of laser illuminated projectors (without the LEDs).
At the top of the heap is the RGB laser, aka “pure” laser technology. Here individual red, green, and blue laser diodes deliver light directly to the optical path of a core chip technology. It is light emitted in a very narrow band of discrete frequencies and permits a color space that exceeds that of Adobe RGB. It can exceed 60,000 lumen light output and is used in specialty applications as well as higher end digital cinema.
The most prolific advances we are seeing in larger venue projection, is what is known as the laser phosphor approach. These typically use a blue laser (or in some cases two), directed through a set of dichroic filters and utilize a phosphor wheel to extrapolate red and green elements. Approaches differ slightly but laser phosphor variations work for DLP as well as LCD and LCoS chip technologies. In terms of light output, laser phosphor projectors start where LED/Laser leaves off, at 4,000 lumens… and at the higher end, are typically in the 10,000 to 12,000 range. Barco has recently announced a model for later this year that goes up to 27,000 lumens pushing that 30,000 lumen target. Now we are talking about the sweet spot of rental and staging applications where laser phosphor projectors can be used individually (or stacked to increase light output), and the good news is that there is no need to change out lamps at the most awkward moments. One caveat here is that the phosphor wheels will have a limited lifetime but they will last far beyond when a traditional lamp gives up the ghost.
One topic that has been kicked around a lot over the last few years is high frame rate (HFR). Ultimately it boils down to the human eye, and how we see. The human eye is capable of differentiating between approximately 10 and 12 still images per second, before it starts just seeing it as motion. Once the frame rate gets over 18 FPS, the motion effect takes over and your brain is tricked into thinking that these individual images are actually a seamlessly moving scene. If the frame rate is too slow then the motion looked jagged, so with that in mind, more frame rate must be better! Not so fast, this is the crux of the ongoing HFR controversy.
Much of the debate relates to motion blur. When you observe a fast moving object, you see a loss of detail. Your eyes simply don’t have enough time to clearly focus on detail, and thus motion blurring occurs. When looking at static or slow moving objects there is no loss in visual acuity. In film you get motion blur because you are looking at a series of frames in a small amount of time. Without the effect of motion blur, the progression between frames appears to stutter and this is called the strobing effect. Film purists still criticize the lack of blur and strobing artifacts in HFR and claim the images are off putting, look fake, and “non-cinema like”. Some refer to it as the “soap opera” effect. This certainly was the response of many to Peter Jackson’s The Hobbit shot in 48 FPS. Sounds a bit like the argument about 35MM film versus digital cinema and vinyl versus a CD in audio of years gone by.
On the upside, people tend to get used to the new frame rates quickly and the images actually contain 2X more motion and spatial detail than at 24FPS, allowing them to become much more lifelike (especially in live action). Part of this is because both motion information and spatial information are integrated together in the signal. On the downside, with so much more detail, HFR makes things that are not real look even less real. Think of this complaint in terms of CGI images, and both sets and actor makeup. In short, the discussion continues and there remain two camps on opposing sides of HFR adoption. Arguments aside, higher frame rates do look more real and in the process, as movement increments decrease significantly, so does flicker and eye strain. HFR is growing in acceptance and the benefits outweigh the drawbacks.
Far less controversial is the topic of high dynamic range or HDR and ultra-high definition or UHD. This begs the question of what is HDR and UHD that is expected to grow 9 fold over the next three years? In compatible sets and source material, HDR removes the limitations of older video signals by increasing overall dynamic range. This includes the ability to expand brightness, contrast, and color distribution from a wider gamut of color and brightness. At its core, HDR video contains more data to describe more steps in between the extremes. This means that on compatible displays, very bright objects and very dark objects on the same screen at the same time can be shown as such, with all the expanded and unprocessed steps in between. Think about it as more shades of gray. In addition, with an expanded color gamut or color space, deeper and more vivid reds, greens, and blues, and more shades in between, can be produced. In visual terms more shades of brightness and color can be shown, thus providing a lot more image detail for the viewer.
Of course all of this increased dynamic range (picture information) will entail increased data and standard Blu-ray discs cannot hold all the HDR information. To address this and other format and data issues, the UHD Alliance, a consortium of over 35 manufacturers and content creators was formed. One of their missions is to provide a new Ultra HD Blu-ray standard and also address 4K and signal distribution without requiring a super-fast internet connection. Online streaming will still be a valid way to offer 4K and HDR video, but Ultra HD Blu-ray provides a physical and broadly accessible way to get it.
From a display technology perspective, in order to receive the UHD Alliance Premium Logo the device must meet or exceed the following specifications:
- Image resolution of 3840 x 2160 aka UHD
- Color bit depth of 10 bits
- Wide color gamut
- Signal input: BT.2020 color representation
- Display reproduction of more that 90-% of P3 colors
- High dynamic range
- SMPTE ST2084 EOTF
- A combination of peak brightness and black level-either
- More than 1000 nits peak brightness and less than 0,05 nits black level or
- More than 540 nits peak brightness and less than 0.0005 nits black level
There you have it. From a resolution point of view, we are in the era of 4K and looking beyond that. Projectors will be increasingly illuminated using solid state systems that takes lamp replacement out of the equation. Although not as hot a topic as it once was, high frame rates are going to continue to grow. Last but not least, HDR and UHD will take our picture information and quality level to the next plateau of enjoyment. As a fan of all displays but projectors in particular, all I can say is that I am enjoying the resurgence of the viewer being the main focal point and now more than ever before, what the content creator dreamed can be shown on screen, both big and small.