AV9000 Checklist Item Under Test: 6.3.16: The displayed image height relative to farthest viewer ratio has been measured: ____ (recommended ratio, 1:6) Record each, compare to recommended ratio.
Reasoning: Digital signage plays a huge role in retail environments, and content is king. However, if no one can read that content, it’s basically useless. As AV service providers, we need to make sure our client’s message can reach its intended audience clearly, comfortably and effectively. We can adjust three variables to this end: distance to the farthest viewer, image height and size of the content on the screen. By understanding our client’s needs fully, we can adjust these variables so the content can be ingested easily by the entire intended audience.
The Story: When I think of retail environments, I think of digital signage. When I think of digital signage, I think of readable content. When I think of readable content, I think of properly sized displays. When I think of properly sized displays, I used to think of the 4/6/8 Rule…but that is so Q1/2017. Now, when I think of properly sized displays, I think of DISCAS! And I don’t know about you, but I am excited.
InfoComm has come out with its new standard for display viewability, ANSI/INFOCOMM V202.01:2016 Display Image Size for 2D Content in Audiovisual Systems, or more affectionately referred to as DISCAS by those “in the know.” Instead of the image size being determined only by task and how far away the farthest viewer is from the screen, the new standard takes into account not only task and farthest viewer but, more importantly, what is actually to be shown on the screen. It may seem like a small, obvious change, but it is brilliant in its simplicity.
At the heart of the new standard is something called Percent Element Height (%EH). An element is an object on the screen that a viewer must be able to see clearly. %EH is the percentage of the screen height that the element takes up. If we are mostly dealing with text, an element would be the height of a lower-case letter. If we are dealing with drawings, an element might be the size of a pixel. Either way, basing the screen size on what the users actually have to see is a powerful design criterion.
For most of AV design, users are most concerned with Basic Decision Making tasks, such as reading text or looking at spreadsheets. In order to find the %EH for these users, we should ask for their worst-case scenario. This would be the busiest spreadsheet they would ever want to show with the system, or the most dense document they would ever expect users to have to read. As designers, we could take that sheet and find an accurate, client-specific %EH that could be applied to all their systems to provide their users with a consistent, readable experience across all of their conference rooms.
The calculations included in the standard are based on other ergonomic ANSI standards regarding human factors. The gist of the calculations for image height for basic decision-making tasks is that the farthest viewer should be less than 200x %EH multiplied by the image height. Or, written a different way, the image height should be larger than the distance to the farthest viewer divided by 200x %EH:
IH = FV / (%EH x 200)
- IH is the Image Height
- FV is the distance from the screen to the Farthest Viewer
- %EH is Percent Element Height
- 200 is the Acuity Factor for Basic Decision-Making Tasks
This is fairly easy to test out with your phone or your laptop. Treat yourself like a client and ask yourself to bring up the gnarliest document you can stomach on your screen. Then, get a comfortable distance away from it, somewhere between where your eyes cross from strain and where you can count pixels. Measure that distance as the FV in the equation. I happen to have the DISCAS standard up on my screen. My FV is roughly 12 inches from my screen to my peepers, when I have to read the fine print. Next step would be to measure the %EH. I have a modest 15-inch laptop with a screen height of about 7.625 inches. A lower-case letter on my display is about 1/16-inch (or 0.0625 inch). So, my rough %EH is 0.0625/7.625 = 0.008, or 0.8 percent.
Now the big question: Is my laptop Image Height (IH) greater than my preferred Farthest Viewer (FV) distance, divided by my %EH x 200?! Do I have a properly sized laptop screen? Do I sit a reasonable distance away from my laptop to read all that good AV knowledge?
IH = FV / (%EH x 200)
Is 7.625 (IH) >= 12 (FV)/(0.008 (%EH) x 200)?
Based on my “farthest viewing distance” of 12 inches for all that fine print, my screen should be 7½-inches high. It’s a little more than that, so we are in the clear. (Thank goodness!) However, this type of empirical testing should be carried out to make sure people can comfortably read what will be put on the screen, and to make sure that the standard actually makes sense.
For retail environments with digital signage, we have a lot of variables to play with using this standard. If the farthest viewer (someone across a corridor) is fixed, we can adjust the image height and %EH. We can try to convince our clients that 100-inch-diagonal digital signage displays will give them the flexibility to easily reach all people passing by the display. However, this might not be feasible, either because of cost, real estate or existing conditions. So, the last variable we can play with is %EH. Basically, we can tell the content creators that any text that takes up less than five percent (for example) of the height of the screen is wasted space, and won’t be readable by the passersby. That is useful information.
Users may not like to hear how much a large display will cost. They might also not like to hear that it would be easier to reach people if their corridors were skinnier. However, if you tell them their message will fall on deaf ears blind eyes if it doesn’t take up “this much” of the screen…well, now they have something easy to work with. Shifting away from just tasks to include what people will be viewing on the screen is a great move on InfoComm’s part. It’s one of those elegant solutions that make so much sense, it’s hard to understand why we didn’t do it that way from the beginning.