For many years, when someone asked us, “How big should my screen be?” we have used basic rules of thumb, based on the size of the audience area and the projection screen format (s) to be used, to arrive at an answer. We recommended a viewing image height of one sixth, one fourth, one half, or one third the distance from the screen to either the furthest or optimum seat, depending on the screen format (4:3. 16:9, etc.). This should allow the screen to be large enough so those in the back row can read the subject matter easily, but not so large as to overwhelm the closest viewer.
This has always been a good general way to get close to the proper screen size. Some companies and systems designers have used slightly different methods of arriving at the optimum size for a video display, whether projection screens or flat panels.
Sometimes it seems like no thought was given to proper size at all. We’ve all been in those meetings when we’re expected to see a TV screen way up in the front of the room. Or where the screen is large, but not large enough to read that spreadsheet.
This past year, InfoComm International has been looking at the question of determining correct display image sizes and relative viewing positions, with the goal of developing an ANSI standard. Last month, InfoComm’s Standards Committee released a draft of the proposed standard, entitled “Display Image Size for 2D Content in Audiovisual Systems,” and is asking those in the AV industry to review and comment on it.
“Properly sizing images for an audience that is making basic or analytical decisions cuts across all industry segments. InfoComm’s Standard Steering Committee saw the opportunity to help with the task and to create a scalable solution to an age-old problem,” according to Ann Brigida, CTS, the Director of Standards for InfoComm International. “The old best practices were based on technologies that are no longer in use today in most places and they just didn’t scale well. As resolution increases, the problem of appropriate content size or viewing locations increases as well.”
One difference in the display size standard is consideration for what the screen and space will be used for: basic decision making, analytical decision making, or both. These are expanded versions of categories taken from InfoComm’s ANSI/INFOCOMM 3M-2011 Projected Image System Contrast Ratio (PISCR) standard.
Depending on the category selected, the standard considers variables including Element Height (size of elements in the content—think font size, for instance); Acuity Factor (relating to our ability to discern objects in the image); Image Offset (the difference between the height from the floor to the bottom of the image and the viewing height); Vertical Viewing Factor (the sum of the Image Height and the Image Offset); and more.
The standard provides the necessary formulas to calculate the screen size using information including Farthest Viewer Distance, Minimum Image Height, Element Height, Vertical Image Resolution, and other measurements.
In the end, having an ANSI standard for screen size should be a good thing. In most cases, I think people will find that larger display sizes are required under the standard—so projection will be needed in more rooms—and we’ll be glad to help fill those needs. Plus, it ensures that any system meeting this standard (and the PISCR standard) will provide the best experience and performance.
Or, to put it another, simpler way: Everyone will be able to see what’s happening on the screen.
The new standard will not apply to all areas—it’s not intended for single-user displays (computer monitors), 3D images, Full Motion Video, curved displays, or tilted screens. There are other caveats as well, which you will find in the standard.
InfoComm is now soliciting industry comments on the proposal. So far, Brigida says feedback received thus far has been very positive.
“The work of the task group gives the industry a practical, easy solution to figuring out farthest and closest viewing, viewing angles, content size requirements, and of course, proper display size,” she says. “The formulas have all been created. We’re working on a web application so you can just plug numbers in to get to the variable you’re missing.”
So, what do you think about how well InfoComm has done in developing this standard? Click here to find out, and to make your comments: www.infocomm.org/publicreview.
