Big ideas need a big canvas, and in order to reach an audience you need to display your content over a much larger area than a standard computer screen. For many that means a large-format display (LFD) or videowall.
Traditionally an LFD was what it said on the tin – a single display screen in a jumbo size.
“LFDs are designed for larger audiences, such as in classrooms or boardrooms,” says Wayne Clark, managing director of Install AV. “Sizes range from around 32in up to Samsung’s 110in Ultra HDTV. Sizes are very much increasing, driven by the demand to replace ageing projector systems with reliable, sharp, clear images without sacrificing screen size.”
In practice many manufacturers’ LFD ranges actually top out slightly smaller, typically at 98in, with anything larger being regarded as too expensive to produce and too cumbersome to install.
If a single-panel LFD is large enough for your application then it will almost certainly be the cheapest and simplest display option. How large is large enough? It depends on what is being viewed and from what distance. “For general viewing a rule of thumb is that the furthest viewer should be no further back than six times the height of the screen,” says Clark. “If you’re studying technical drawings that may need to be reduced to four times.”
When a single panel is not large enough you need to consider a videowall, which spreads the image across a number of display panels or tiles. Videowalls can be any size and shape – that’s one of their attractions – although maintaining a regular shape, such as two panels by two or three by three, means you can display regular-shaped content without requiring complex “scaling” (re-jigging to make it fit).
However, according to Peter van Dijk, senior business development manager at Mitsubishi Electric Europe, the distinction between LFD and videowall is becoming less clear cut. “With the advent of ultra-narrow pixel pitch LED of 0.9mm or less, the distinction between modular videowalls and single unit large flat displays is becoming much less easy to define, as LED allows the creation of virtually seamless LFDs of any size.”
It’s all about bezels, those annoying gaps around the edge of each display panel that can give conventional videowalls a chequerboard appearance. Traditional LCD (liquid crystal display) videowalls require a frame (or bezel) around each display surface. Bezels have become narrower and less obtrusive over time, but that chequerboard effect is still there.
With the newest display technology, LED (light-emitting diode), the display surface goes right to the edge of the panel. This eliminates bezels and creates the illusion of a single display stretching as far as the eye can see (sometimes almost literally).
It is just an illusion, though. The viewer may see an unbroken image but, like the proverbial swimming swan, beneath the smooth surface there is still a lot of energetic paddling to make it all happen.
“Modern videowalls are a complex hybrid of display hardware, IT infrastructure and software,” says van Dijk. “Much of the image processing that’s required to display images across multiple screens can take place on board the individual display units, in the case of compact videowalls, or in much more powerful outboard hardware controllers for higher-specification displays.
“The very latest systems use multiple mini-computers called NUCs to create a processing environment which can scale dynamically as demands on individual parts of the system increase – for example scaling vector-based content such as a SCADA (supervisory control and data acquisition) diagram from an individual display to the entire videowall with no loss of quality.”
This processing complexity means that, although LFDs are very good at displaying a single image, they come nowhere near the capabilities of a videowall in ability to display multiple sources in multiple sizes, van Dijk adds.
Because videowalls are entirely modular the sky’s the limit when it comes to size. As Thomas Walter, strategic product marketing manager at NEC Display Solutions Europe, succinctly puts it, “The scalability of a videowall is only restricted by the space available, the supporting infrastructure and the budget.”
The bigger the solution, the more complex it becomes to install and run. “Small, two or four screen videowalls can be installed to most walls with relatively light structural work, or even to free standing or mobile support structures,” says Stuart Davidson, technical services director at AVMI. “But large scale videowalls can consume lots of power, create lots of heat and weigh many hundreds of kilograms, so detailed coordination with base build construction and mechanical and electrical teams is essential.
“Perfect flat panel alignment with uniform colour and brightness across a videowall also becomes more complex and time consuming as the size increases.”
Large display areas
Larger display areas may also require higher-resolution content. “The bigger you make a screen the more pixellated or blurred an image can become,” says Clark. “A 1080P image from a digital signage player may look great on a single 65in screen, but displaying it on a 3m wide videowall will mean each pixel of the content is much larger, so the image won’t look as clear and sharp.”
The right mounting solutions can take much of the pain out of installing, positioning and aligning large videowalls, says Keith Dutch, EMEA managing director at Peerless-AV. “Full service videowall mounts offer time saving features such as tool-less micro adjustment, integrated cable management, custom wall plate spacers and easy, quick release access to any display for servicing and maintenance.”
One attraction of videowalls is that, being modular, their shape can be custom designed to maximise the impact and use of space. “A long ribbon effect, for instance, might be more appropriate above tills or a check-in area, which can be achieved using smaller format displays alongside one another,” says Walter.
Conventional videowalls had to be flat, but LED and OLED (organic LED) technologies are breaking the mould – or at least bending it. “OLED has opened up opportunities for videowalls to be curved, circular and created in convex or concave shapes due to its ultra-thin and flexible characteristics,” says Pete Mytton-Bayley, B2B pre-technical sales engineer at LG Electronics. “There are more creative shapes than ever on the market, so do your research and select displays with the best aspect ratio for your ideal content and space.”
LFDs tend to come in standard 16:9 aspect ratios, but there is a trend towards panels with more creative aspect ratios, such as stretch displays for digital signage and retail, Mytton-Bayley adds.
Good old LCD technology currently retains the top spot in videowall sales. “It offers a lower initial cost, a higher resolution for a given space, a much wider selection of display options and a variety of control systems,” says a spokesperson for Daktronics. “The disadvantages are a significantly shorter lifespan, low brightness for competing in high ambient light environments, high power consumption, and limited options for aspect ratios as LCDs typically [only] come in a 16:9 format.”
But snazzier, bezel-free LED is becoming increasingly prominent, especially in retail, transport and prestige corporate applications. “Offering an excellent total cost of ownership, LED brings consistent, long lasting performance with vibrant colours and brightness,” says Walter. “Currently the initial investment is much greater than LCD, but for premium applications, fine pixel pitch LED is a compelling option. Where viewing distances are great, such as in transport hubs or outdoors, large-pixel LED delivers brightness that attracts viewers.”
LED particularly lends itself to customised installations, says Liam Winter, product director at Absen Europe. “LED lets you customise brightness levels to match the ambient light, as well as the refresh rate (some LEDs offer 1,920Hz and over). LED modules are typically smaller than LCD panels so they’re more likely to be a right fit for a specific location, and they can be serviced from the front or the rear.”
LED’s younger brother, OLED, is also starting to make waves, thanks to its sharp images, quality colours, high contrast and quick refresh (good for fast-action video). Because pixels can be switched off individually, OLED can also produce very deep blacks. However, the technology remains expensive, and there are concerns about the risk of image retention (where a static image eventually leaves a permanent stain on the display itself).
As we observed earlier, the development of narrow pixel pitch (NPP) LED is enabling the technology to penetrate markets where close-up viewing is a requirement. The finest LEDs are now below 1mm in pitch, although they still can’t quite match the 0.5mm-0.6mm of LCD.
Pixel pitch – the distance between the individual dots (pixels) that form the image – is important because it dictates the maximum resolution of a given size of panel and affects how close viewers can get without the image looking grainy. A common rule of thumb is a minimum viewing distance of one metre for every 1mm of pixel pitch, says Davidson.
In the specialised world of command and control rooms, DLP (digital light processing) rear projection cubes remain the mainstay, according to van Dijk. “DLP is a stable, mature technology that offers excellent reliability and lifespans of up to 15 years of continuous use. Unlike DLP, LCD can suffer from image sticking when static content is displayed for long periods, and it will typically have a much shorter lifespan.”
Interactivity with LFDs and even videowalls is becoming a more common requirement. “LFDs are available with fully integrated physical touch technologies such as infrared (IR) and projected capacitive touch (PCAP),” says Dutch. “With a videowall interactivity is typically more complex as custom touch frames are required. Other ways to interact include touch foils and overlays, Xbox Connect, QR codes and mobile devices.”
A number of other built-in features of videowalls are worth taking into account, according to Mytton-Bayley. “Built-in speakers give the ability to play sound, while a built-in system-on-chip allows the use of third-party signage software, and onboard memory means users can save imagery in various formats directly to the screen. These connectivity features are becoming increasingly important for digital signage and networked applications, while displays with Bluetooth capability allow digital advertising to be streamed via connected devices.”
Before we finish it’s only fair to point out that LFDs and videowalls are not the only game in town. Projection has become much brighter and more reliable with the advent of laser technology, and where viable is generally reckoned to be the most cost-effective way of displaying content over a large area, so it’s definitely worth considering.
And finally, a riddle. Why is an LFD or videowall like a pet? Because it will probably cost you far more to keep than to buy.
“Just 30% of the total cost is represented by the initial purchase price,” says Walter. “The other 70% is spent on operational costs including power consumption, maintenance and device management, but this proportion is often ignored. So it’s vital to make your purchase decision based on reliability, low failure rates, lowest power consumption, lowest potential for failure through removal of unnecessary cables, and upgradability of the player performance, which will all help to ensure the lowest operational costs.”