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4K-8K-16K Stewart is There

By Alan C. Brawn CTS, ISF, AIA

To all the fans of home theatre and the history surrounding its evolution, you should be proud of yourselves. With all due respect to other bastions of display technologies, it has been the residential industry that has nurtured and brought forth the developments that we see as mainstream across of all segments today. The residential community did not fall victim to the early days of cheap lumens and be satisfied with simply coming out of the darkness of the CRT days. The home theater crowd demanded the colorimetry and contrast levels capable with a CRT projector but in a higher brightness form. They were the first to embrace display calibration to standards. Proof is no further away than the Image Science Foundation and the work done on color space, contrast, and image fidelity as well as active end user community sites like the AV Science Forum.

From a projection screen perspective, it was the residential community that understood the benefits and the limitations of matte white screens and wanted more. They drove the development of ambient lighting controls to a much more sophisticated level. To supplement their demand and pushing the envelope for better image quality, and with necessity being the mother of invention, this energized the development of gray screen technologies with no better example than the iconic Stewart Filmscreen Grayhawk screen. It did the seemingly impossible in that it enhanced contrast in a home theatre environment while introducing the first levels of ambient light rejection.

The latest technological trend that the home theater aficionados have been the first to embrace is 4K resolution. As expected, there are some nay-sayers out there and we have all seen articles with titles like “Is 4K Really Necessary?” and “Barriers to 4K”. At some level, most of these articles have legitimacy in the questions they raise. They write about the current lack of availability of 4K source material and the bandwidth that is needed to stream 4K while others mention that 4K is best when viewed at close proximity and claim there is little visible difference at longer viewing distances. There is no argument that we are in the midst of an evolution of source material (i.e. UHD and HDR lead by the consumer market once again) not to mention available bandwidth, but the issue of visible differences is one that begs for more discussion and involves the science of visual acuity. One way to consider all of this is to think of retina displays in smart phones and more information on screen rather than simply pixel count. If you look at a 1080P image side by side with a 4K image, you will immediately see the difference. Let’s take a quick look at the science behind all of this.

Understanding Pixels

In order for us to understand the issue of resolution and its effect on the viewer, let’s start with pixels. We all understand the more pixels there are, the smaller they become, resulting in more overall picture information that can be displayed on a screen. This is true but too simplistic. Ultimately it boils down to what the human eye can resolve and begs the question, so just what can we see? For the technical types out there, lets refer back to the Snellen eye chart to measure 20/20 human vison. We learn that the human eye resolves one arch minute of information. An arc minute is just a subdivision of 1 arc degree and there are 360 arc degrees in a complete circle and 60 arc minutes in each arc degree. And as you can see from the diagram below, we can also subtend 1 arc minute because someone with 20/20 vision can see that the letter E on the eye chart. In short, that’s what we actually see but let’s do a little bit more math and relate it to pixels and then what we see on screen.

There are 10,800 arc minutes in 180 degrees of viewing. So the eye has a limited resolution of one arc minute and would require no less than 10,800 pixels wide. To achieve similar horizontal resolution with 1920 x 1080 projectors would require 10,800 divided by 1920 H pixels per projector which is 5.6 projectors across edge to edge and 7000/1080 or 6.5 projectors vertically- and that’s without blending losses. So we would need about 6 x 7 or 42 of these HD projectors minimum to match human acuity. Clearly that is not too practical, and very expensive but it gives us some idea of what the human eye can see. Perhaps now the 4K, 8K, and 16K displays begin to make more sense if we think in terms of the human eye and what it is capable of seeing.

Image Resolution

If we turn our attention to the display devices that create what we see and keep in mind the “holy grail” of what the human eye can resolve, let’s take a look at resolution from another perspective. Image resolution correlates directly to detail in an image. All else being equal, higher resolution means more image detail and the closer we get to visual acuity.

There exists some confusion about resolution and some think that it only relates to pixel density or the number of pixels on a given image or chip. The number of pixels does correlate to the amount of information within the image. It is true that a digital chip at 1920 x 1080 provides the core capacity for higher resolution when compared to a chip with 1024 x 768 resolution but the resolution we see on screen does not stop there. Other variables come into play such as the light engine, processor, both internal and exit optics as well as the projection screen.

As we illustrated in a prior example, 1920 x 1080 does not attain the threshold of visual acuity. Here are the current standards that are being embraced today and for the foreseeable future and it relates to a combination of visual acuity and overall source information on screen.

  • 1920×1080: HD
  • 2048×1080: 2K Digital Cinema
  • 3840x2160: 4K UHDTV
  • 4096×2160: 4K Digital Cinema
  • 7680×4320: 8K UHDTV
  • 15360x8640: 16K Digital Cinema

8K and Beyond

Lest it appear to be overstating the case in support of higher resolutions and dynamic range, we can see the recent developments in the real world of the UHD standard. It begins at 4K (3840 x 2160P) and goes up to 8K (76080 x 4320P) and embraces not only pixel density but advances in all optics, processors, and source material that can take advantage of higher resolution and high dynamic rate (HDR). 4K resolution is here and 8K is the successor with 16K waiting in the wings. As a point of reference, 8K UHD has two times the horizontal and vertical resolution of the 4K UHD with four times as many pixels overall, or sixteen times as many pixels as Full HD at 1920 x 1080.

We understand that there is little 8K source material available today but an 8K display can also be used with the purpose of enhancing lesser resolution videos with a combination of technique currently used in video and film editing. Resolutions such as 8K allows filmmakers to shoot in a high resolution and edit as they see fit to the appropriate size. NHK, Sony and Red Digital Cinema are among those that are embracing 8K and film makers are pushing for more.

Choosing the Right Screen Material

All of this increased resolution and dynamic range goes a long way toward images that approach what the human eye can see but there is another partner in the equation and that is the screen on which the enhanced images will be shown. As in all things AV related, one size does not fit all. It is the combination of the projector, the source material, the screen, and ambient light that is combined to create what we see. What is sometimes overlooked and deserves more consideration, is that the screen reflecting the image of the projector and the source material back to the viewers can be the weak link in the chain and to say the least, all are not created equal. As source material gets better, resolution increases. and projectors improve, it is the responsibility of the screen to keep faith with all of these elements and improvements. It is in this area that Stewart Filmscreen fills in the void and delivers on the promise of true image fidelity, but not just for 4K as it exists today, but to 8K and even beyond 16K for future applications.

In this regard, Stewart Filmscreen continues to be the technology leader in screen surfaces and is dedicated to that being the strongest link in the chain. Knowing what we now know about visual acuity, we can do a bit more simple math to make the point of future proofing a home theater system. If we use a Stewart ten-foot-wide screen as an example, it is equal to 3048 millimeters. Scientific testing shows that Stewart Filmscreen fabrics are capable of resolving 6 line pairs or arc minutes per millimeter. So if we take 3048 millimeters and multiply that by 6, we get a product of 18,288 possible pixel addresses per ten feet of screen width. This is greater than the resolution furnished by a 16K projector if one existed.

As usual, it is the residential community and home theater aficionados that will lead the way in understanding and embracing the implications of things like UHD and HDR and ultimately the part the screen will play in this equation. Since Stewart fabrics are able to resolve resolutions well beyond the limits of the human eye as we move beyond 4K to 8K and then to 16K and beyond, Stewart Filmscreen ensures the screen is not the limiting factor. Bring on UHD and HDR and be prepared to project the best knowing that Stewart Filmscreen will show you the best in return!

Stewart fabrics are able to resolve resolutions well beyond the limit of the human eye. As we progress from 8K to 16K and beyond, Stewart Filmscreen is ready and waiting. Give us your best and we will show you the best in return!

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