Posted in education
on May 4, 2016 11:20 am EDT
LED Video Wall Design: Resolving Issues of Resolution
In an excerpt from a report on LED video walls and their applicability in church design and usage, Church Designer's reporter focuses on the all-important topic of resolution.
Bethel World Outreach, Nashville, Tenn., courtesy of PixelFlex.
Like all AVL technologies, LED video walls have their own peculiarities that users need to be aware of to maximize their investments and benefits. The first decision users must make is the resolution of the displays. The tighter the pixel pitch (the center-to-center spacing between each LED, both vertical and horizontal, measured in millimeters), the finer the resolution of the overall images. Pixel pitch is an esthetic choice—think of the difference between 720 and 1080, or 1080 and 4K resolution—but also of the physical location of the wall in relation to where viewers will be.
“It’s crucial to choose the right pixel pitch for the environment,” stresses Nicholas Fazio, product manager for Christie Digital in Cypress, Calif. “The smaller the pixel pitch, the closer your minimum viewing distance can be. If you’re too close to a video panel with a high pitch, the images will look pixelated—you’ll be able to see the individual LEDs that make up the image rather than the image as a whole. The ability to project a good-looking, coherent image is a balance between pixel pitch and viewing distance.”
Image courtesy of Vichailao.
Fazio says an industry rule of thumb has been to allow one meter of viewing distance for every millimeter of pixel pitch. So, if a pixel pitch is 5.2 millimeters, the optimal minimum viewing distance is 5.2 meters, or about 17 feet. He adds that Christie uses a different benchmark, depending on the nature of the content intended for the video wall, of 2.5 meters per pixel, so that same pixel count would bring the optimal distance to 13 meters.
Fazio says an industry rule of thumb has been to allow one meter of viewing distance for every millimeter of pixel pitch.
Fazio reports that he’s seeing most of the LED video-wall activity in houses of worship that have high ambient light conditions, and that have a number of services and other activities throughout the week. That’s where the fastest return on investment will occur. “Churches with very controlled-lighting environments will still derive a lot of benefit from conventional projection,” he says. “But as LED costs continue to decline, the benefits of them will start to make more sense to more and more churches.”
Those benefits include lower operating costs, not just from the elimination of projection lamps but also from lower power consumption. However, Fazio cautions, users need to carefully measure just how much power/illumination they really need in their spaces. “You don’t want to run it at 100% power, because that will shorten the lifespan of the LEDs,” he says. More typically, power levels between 35%-45% of maximum will produce sufficient brightness. On the other hand, power settings that are two low can cause bit depth to collapse, with anything other than the brightest elements in the content being lost in darkness. “Blues and blacks and grays start to look the same,” he says. “Power balance is critical to a good visual outcome.”
Dave Cook, production chief engineer at Willow Creek Community Church in South Barrington, Ill., says he’s able to operate successfully at even lower average power levels, closer to 25%, in the church’s larger venues, thanks to a complete lack of ambient light. On the other hand, in the one room of the four where LED video walls are installed that has skylights, it runs closer to 50%. “Power settings are really mostly dependent upon the amount of ambient light,” he says.