Picture quality in projected and display content has never been better. 4K, High Dynamic Range (HDR), Wide Color Gamut (WCG), and High Frame Rate (HFR) are recently developed or new technologies that are having a major impact on images in AV and digital signage.
This summer, AV industry expert Alan C. Brawn of Brawn Consulting visited Draper to address these and other issues with our AV staff. Alan has long been a friend of Draper and sent us a copy of a new article he’s written on these technologies and their impact on digital signage. Although much of what Alan says is in terms of displays, the same technologies and benefits are there in projectors and screens, so we decided to share.
Alan’s piece “Digital Signage: Images to Remember” was originally written for Digital Signage Magazine.
To state the obvious, digital signage is primarily a visual medium. As it has evolved over the last decade it has transcended advertising and retail applications. Digital signage has become a communication tool to reach us at work and at play, wherever we are, whenever we want, and on a device of our choosing. At the macro level digital signage is about impressions, but at the micro level, it is about recall.
For both impressions and recall, it boils down to the image. This is further broken down into the content on the screen and the quality of the image that we see. A lot has been written about content, but we want to look at the image itself, and how this affects both the content creators and the impact on the viewer. We have all heard the euphemisms such as you only get one chance to make a first impression, what you see is what you get, and perception is reality. Apply all of those to the topic of image quality, and viewer impact and recollection.
As we begin our little tutorial on image quality, keep in mind that screens of varied sizes will require different resolutions, contrast, and brightness for people to appreciate a good viewing experience. Over a decade ago, image quality came more pervasively to the forefront with the introduction of the Apple iPhone and their Retina display. The goal was to make the display of text and images extremely crisp, so pixels were not visible to the naked eye. This allowed small displays to rival the smooth curves and sharpness of printed text and the naturalness of photographic prints. When introducing the iPhone 4, Steve Jobs noted that this was for a device held 10 to 12 inches from the eye. What we learned from this is that as the distance of the viewer from the screen increased, the resolution, contrast, and brightness had to increase, as well.
Most of the digital signage that we are exposed to each day goes well above and beyond mobile devices. What we see in the stores, restaurants, offices, and public places are “big” screens typically starting at 32” diagonal sizes all the way to huge videowalls. Understand that as screens get larger, pixels become more and more visible. In short, the picture gets bigger and the pixels get bigger. Going back to the Retina display concept, the goal for the viewer is the same for larger screens and that is to make the pixels unnoticeable. Migrating from 1080P resolution displays up to 4K devices provides several missing pieces to the puzzle.
4K is known as Ultra High Definition (UHD), while 1080P is Full High Definition (FHD). 4K UHD has a considerably higher resolution than 1080P FHD video. 4K resolution is 3840 x 2160 pixels, while 1080P consists of 1920 x 1080 pixels. Most of the screens we use in digital signage feature an aspect ratio of 16:9 (image width to height), and 4K contains almost four times the number of pixels on a screen compared with 1080P technology. In sheer numbers, this is more than eight million pixels for 4K, and just two million pixels for 1080P. This significant difference allows 4K to have some important advantages over the quality of 1080P video or graphics.
The obvious advantage is the ability to resolve extra fine detail, even at a close viewing distances … but it does not stop there. From a content production point of view, the creators can scale down higher resolution recordings to regular HD and other formats while retaining the high contrast and highly detailed quality of the original. In the case of 4K content, one may wish to downscale to a 1080P high definition output for bandwidth reasons. Tests have shown that when comparing the final video quality of a 4K video which has been downscaled to 1080P, the picture is noticeably more detailed than could have resulted from originally creating the recording in 1080P.
The story may begin with pixels but does not end there. The more complete explanation goes to the understanding of the major elements of 4K UHD that make is so memorable. To the first order it boils down to how close an image is to what the human eye can actually see. We will save your eyes glossing over and won’t go into visual acuity, and the science of what the human eye can resolve. Suffice it to say that the closer we get in our images to what we see in nature, the more pleasing and memorable the viewing experience will be.
What completes the image experience is High Dynamic Range (HDR), Wide Color Gamut (WCG), and High Frame Rate (HFR) in both the content that is created and the ability of displays to show that content. One without the other does not result in all that the image was intended to be. As one writer put it, “Who cares if you have four times the amount of pixels on the screen if they’re all awful in terms of color and contrast? What HDR is promising is better pixels. For bright whites to be brighter, for dark blacks to be darker and 10-bit panels to finally display all 1 billion colors.”
HDR goes beyond the limitations of HD and provides brightness and color across a much wider range. HDR content has more information in the recording and HDR capable displays accurately show images from that wider gamut of color and brightness. This means that the range of very bright and very dark objects on the screen can be shown with all the necessary steps in between as the content creator intended without image processing. Images can show more shades of gray in between extremes. IHS Markit research reports that HDR display shipments to soar 300% by 2021!
Similarly, HDR content and compatible displays have WCG that produces deeper and more vivid reds, greens, and blues, and show more shades in between. If we look at basic HD, it shows 35% of what the human eye can see in terms of color palette whereas WCG capability produces 75% of what we see. Also, going from 8-bit color processing to a minimum of 10-bit provides a smooth transition between color shades.
Will Greenwald in PC Magazine sums it up nicely. “Deep shadows aren’t simply black voids; more details can be seen in the darkness, while the picture stays very dark. Bright shots aren’t simply sunny, vivid pictures; fine details in the brightest surfaces remain clear. Vivid objects aren’t simply saturated; more shades of colors can be seen.”
If we include HFR in the mix, (not to be confused with HDR), it describes the ability to reproduce video at 60 or 120 frames per second versus standard television at 30 frames per second. In standard video there can be what is called motion artifacts at 30 FPS as the video is displayed from frame to frame. HFR videos will look far smoother, sharper and realistic, and ultimately improve picture quality drastically.
For those of us in the visual image business, our goal should be the put forth the best images possible. In the Digital Content and Media Certification (DCME) it teaches that “good content applied to a channel at the right location, at the right time, and with the right message, will result in impact”. Impact will depend on the quality of the content displayed as well as the quality of the display. 4K UHD combines all the elements critical to fully realized visual acuity. Content creation parameters are matched with the display’s capability to show images in all their glory. When done properly this falls into the category we all seek. It becomes memorable.
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Source: Blog Posts