Direct-View LED Displays: Questions Answered

Alan Brawn, Principal
Brawn Consulting

One of the hottest topics in the display industry today is direct view LED displays. As point of clarification, using LEDs as the back light for an LCD screen does not make it an LED display… just saying! The goal of our discussion here, is to answer some common questions regarding LED displays, and remove some of the marketing bias. We will begin with a little historical context, and track the evolution of this rapidly developing technology.

The first known report of a light-emitting solid-state diode was made in 1907 by the British scientist H. J. Round. This experiment demonstrated the creation of light through a solid substance, but no practical use was made of this discovery for several decades. The first example of a practical LED was invented by Nick Holonyak, Jr., in 1962 while he was at General Electric. This lead to the launch of commercially available LED lamps in late 1960s, but they were limited to the color red. Additional colors were developed in subsequent years, adding green, yellow, and orange. The first grouping of LEDs used as a display was in 1977, but was monochromatic. This was because at that time there was no efficient blue LEDs available, which were developed in the early 1990s at Nichia. This gave us the ability to manufacture full color direct view LED displays. Fast forward to “modern” times, and there are a wide range of direct view LED products, using high-brightness LEDs to generate a wide spectrum of colors. So as you can see, LEDs are not new… the evolution and acceptance of the technology has increased rapidly over the last decade. We see this in the expanded applications of LEDs in every part of our lives (beyond just displays!), but for discussion here, we will focus on the advancement in fine pixel pitch direct view LED displays.

You will commonly hear direct view LED displays referred to by their pixel pitch (e.g. 4mm, 10mm, 24mm). The pixel pitch correlates to the resolution of the sign. It is dependent upon the distance between each pixel, typically a cluster of three LEDs – one red, one green and one blue. In a fine pixel pitch LED display, these are often combined into a single diode package, to make them even more compact. The distance between pixels is measured in millimeters, and the smaller (or finer) the pitch, the closer together the LEDs are placed. This gives you smoother and more life-like images, offering the ability to view the display at closer distances. Thus, it is the pixel pitch that will determine whether the individual LEDs are seen at a given viewing distance. For example, you can have a 20MM video wall viewed from the highway as you drive past and it would look like a smooth image, but if you were viewing it from up close you would see a pixilated image, with visible individual LEDs. With the advent of fine pixel pitches starting at 10MM and going all the way down to around 1MM (with finer pitches coming soon!), the viewing distance issue is one of application and price… but not availability. In this regard, we have come a long way in a relatively short period of time.

Direct view LEDs are usually broken down into two overall categories: outdoor and indoor. One note on outdoor displays… while they can be dynamic for messaging, most jurisdictions ban full motion as it is distracting to drivers. The selection of both types usually begins with specifying pixel pitch, based on the desired average viewing distance for the application. Outdoor displays are typically viewed at much longer distances, and so range from as coarse as 24MM all the way down to 6MM or so for high end use. LEDs have several advantages over other types of signs, especially in brightness. Competing with high ambient light is a challenge, requiring between 4,000 to 8,000 nits of brightness. LEDs can meet or exceed this, making them stand out very effectively. LEDs are inherently robust, built to last, and stand up to the environment (temperature, dust, moisture).

Indoor displays start around 10MM (but 6MM would be a more reasonable consideration) down to less than 1MM. These are designed for closer viewing distances, and thus much higher resolutions. They are capable of high brightness, well over 1000 nits, for high ambient light conditions indoors. One of the side effects of making such fine pixel pitches is a change in the LEDs used… we must go from discrete diodes used for coarser pixel pitches, to SMD combined packages (placing red, green, and blue emitters into a single LED, as previously mentioned). This limits brightness compared to outdoor grade products, due to heat being more concentrated in the smaller LED. This also makes them difficult to weatherproof, so they are generally not used outdoors.

Of course, the topic of direct view LED would not be complete without discussing price and investment considerations. In terms of outdoor or indoor signage, it is irrefutable that the upfront cost of putting up a direct view LED sign (or an LCD videowall) is more than installing a traditional static sign. The question boils down to the return on investment, and return on objectives. This is where the issues and math become more complex.

The major issue to consider, is the upfront cost of the display and cost to electronically distribute sign content VS. the cost to print and install new static signs regularly. With the higher upfront investment, comes the ability to change your content as much as you like, adapting to changing conditions, promotions, and even the weather at will… which is impossible to replicate with static signage. This is one of the key arguments long used for justifying (and correctly so!) digital signage. However, an additional consideration that can occasionally be overlooked, is the impact of the digital sign VS. traditional media. This also contributes to the return on investment and return on objectives for the signage project in a meaningful (but not immediately apparent) way. For the purposes of advertising-based digital signage, it boils down to the cost of advertising VS. the viewers that will receive the message of the advertising.

Research shows that outdoor LED sign advertising is an incredibly cost-effective advertising tool compared to traditional methods. This is measured by calculating an advertisement’s cost per 1,000 impressions (commonly abbreviated as CPM). LED signs have an incredibly low CPM, as little as $0.15, in a typical American town. For comparison, an average newspaper CPM is over $7. A low CPM means a business can reach a much broader audience for less money. Per the Small Business Administration, small businesses enhancing their signage with an LED display typically see an increase in business of around 15%. It is important to note that as traditional advertising avenues are in serious decline, all types of signage are on the ascendancy.

When looking at indoor direct view LED displays we have more things to consider. In competition for your signage dollars are static signs, large flat panel displays, LCD video walls, and direct view LED displays. Once again, we cannot refute that the lowest upfront cost signage option is a static sign. Even if you figure in the need to replace the sign with new content and the labor to change it out, it will take some time to recoup the price differential to go digital, depending on your frequency of updates. Some people stop right there… but this may be short sighted. Research shows that digital signage is 10 times more impactful and memorable than a static sign, primarily by being dynamic. This not only levels out the playing field of price, but weighs heavily in favor of digital signage being able to meet your objectives, while providing more options than static signs.

LCD flat panels dominate indoor digital signage, but as they have become more commonplace, we have seen the trend of using larger and larger displays, in a sort of “arms race” to draw viewer attention. Larger displays, properly integrated, add to the customer experience and deliver greater impact… and this has led to the trend of using LCD videowalls. Direct view LED displays can overcome one of the largest objections to LCD videowalls… the bezels. There is no current way to make LCD based videowalls seamless, and while they can be more cost effective, the “look” of the bezels detracts from the overall viewing experience for many. LED displays also tend to be brighter, working better in well-lit retail environments (for example), and can be created in more unusual and fluid shapes than more “building block” style LCD display configurations. This can also demonstrate higher impact, as people become accustomed to the standard 16×9 shape of LCD displays. This all allows LED displays to provide a significant benefit, despite a higher initial cost.

Another common question when evaluating LED displays is that of spares… backup LED tiles or panels purchased from the factory or supplier. This is often recommended by the manufacturer, and it’s not just a play for getting more money from the purchaser. Let’s just say it is a good idea for three reasons… First, if you buy panels all from the same manufacturing run, you will preclude any manufacturing changes that happened between runs at the plant. These can cause a difference in color or brightness between a new panel and the old ones (Especially after they have been in use for a while). Secondly, you avoid any deviation in terms of mounting or size of the new panels. Third, but not least… if you have a panel malfunction or fail, you do not want to wait to have a new panel shipped. Many manufacturers produce LED displays in China, and this means that it can take a while to come from overseas… or be subject to extreme shipping costs.

Are there other platform or performance details or idiosyncrasies that you need to be aware of? Keep in mind that LCD flat panels are cookie cutter in that they are primarily a standard aspect ratio, and one of two resolutions (1080P or 4K). When installing direct view LED displays, the pixel pitch, size, and shape will change the aspect ratio and resolution of the content needed to be delivered to them. This is not a huge challenge, but something that you need to be sensitive to. Most direct view LED displays today can produce as saturated a color gamut as an LCD display, but if a wider gamut is needed for specialized applications, you may need to look at a different display technology. Direct view LED displays can also be somewhat heavier, so consider mounting carefully… also, ensure that you use a good quality mounting system. No two manufacturers of LED tiles use the same configuration, and outdoor tends to be custom built for the application. Indoors becomes somewhat easier, with companies now offering universally capable mounting solutions, but it still requires careful thought.

It is impossible to anticipate every question regarding direct view LED displays but with the onslaught of new players coming into the market, it is also impossible to ignore what is going on. Our crystal ball tells us that this niche will continue to grow as more people on all sides dive into the deep waters of direct view LED.  Applications are already flourishing as people embrace the impact they can achieve. Prices will continue to moderate but still be more expensive than LCD video walls but ultimately you get what you pay for.


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