When considering to purchase a Digital Signage or Electronic Message Center (EMC) LED, what is the ideal configuration? What’s the difference between pixel pitch and pixel composition? There are several different options that are offered for different applications, and for that reason, there is no single “best” LED display for a Digital Signage application.
The “best” will be the closest match between requirements, expectations and sustainability. Navigating the Digital Signage options is a little less complex than understanding LED Video Walls, but there are a few key universal truths. We will discuss an introduction of what to look for when purchasing an outdoor LED sign, and while all the factors provide some service, we will only look at the main few.
What will be displayed?
The first question is to identify the requirements that will be used to define what content will be displayed. Is the idea to display text to update hours and events? Will there be logos or images? Using images is a good way to have full control over how the message is formatted, but that would also require somebody with graphic art skills to create them.
Pixels are important
Let’s start with by looking at pixel composition of a LED display. Dual In-Line Packaging, or DIP, has a separate LEDs for each color. Each pixel consists of 4 LEDs. 2 Red, 1 Green and 1 Blue. Using 2 red LEDs allows for and pixel sharing and better viewing angles (which we will not discuss), and is labeled as 2R1R1B. As LED technology has improved, and to reduce cost, a typical DIP pixel configuration is 1 Red, 1 Green and 1 Blue, labeled as 1R1G1B, has become more standard. Although considered older technology, DIP offers advantages for outdoor displays as being brighter, and having higher reliability rates due to better heat dispersion. To get to higher resolution ranges, the 3 LED bulbs were combined into a single chip, and placed on the circuit board. This is called a Surface-Mount Device, 3-in-1 SMD. They produce a better image, have higher resolutions, and are becoming more common, even for an outdoor application. A 3-in-1 SMD display is a good choice for an outdoor display, unless the known location will be in direct sunlight most of the day.
Pixel pitch
Which brings up pixel pitch. Pixel pitch is the space between the pixels. The closer they are, the better the picture. So the smallest is the best right? Not exactly, with a decrease in space between pixels, means an increase in LEDs, resulting in higher cost, and more power consumption. With a larger pixel pitch, LED displays can take advantage of human persistence of vision. In short terms, this is our ability to stitch the pixels together for a cohesive continuous looking image. Just right, the image looks great. If the pixels are too far apart, or you stand too close, this spacing becomes noticeable. Closer together, or standing further away, improves the image. This is why there is a balance between pixel pitch and viewing distance. Rule of thumb here is very subjective, and varies. Our rule of thumb, and one that can be argued, is 3 * pixel pitch, derived from the 3 feet per meter conversion.
So with all that said, without analyzing all external factors, for a 3′ 8″ x 9′ 5″ LED sign, we would recommend a 3-in-1 SMD with a 10mm pitch to be viewed from the road at 20-30 feet (3 * pixel pitch), or a DIP LED sign with 16mm with a viewing distance of 38-48 feet. There are formulas and calculations to help determine the proper pixel pitch based on viewing distance based on application, but we would reserve anything over 16mm for very large displays, or large viewing distance.
So, we’re all set right? Well, not yet.
Software
We also need to look at the software aspect. How are we going to configure the screen, or change the content? Software is often overlooked. Does it come with an application, or would you need to purchase additional digital signage software? The cheaper Chinese brands often have poorly written, minimal capability software that is updated in an unsecured way. Some brands offer greater flexibility in the software. At a minimum, you should be able to control the display, and enter content. Established manufactures such as Daktronics, will have an advantage over the Chinese brands, as they will have more options and more intuitive software that is easier to use.
Replacement parts
Next we need to look at replacement parts and accessories. One option that should be considered, if available, would be a brightness sensor. This dims the display at night. Some offer a schedule, but the sunrise and sunset change often, and the sensor works best for this. Dimming the display is visually appeasing at night, increases the lifespan, and reduces the power consumption. However, no matter what display you choose, make sure you get spare parts at delivery of your new sign. The industry is moving fast, if you do not get replacement parts now, you may not be able to in the future. Spare tiles, power supplies, louvers, and cables are critical to have on-hand to maintain your LED display, and prevent downtime. When an LED display is manufactured, each batch of LEDs used is a bit unique. LEDs manufactured at different times can produce slightly different color variations. Additionally, as LEDs wear over time, and its output can be affected. An LED sign is made up of several smaller panels. Therefore, when one of these panels fails, or needs to be replaced, the new panel is often noticeably different, as the colors and brightness are not consistent with the rest of the display. You may have seen this when a small block on a display looks different than the rest. To prevent this, make sure spare panels are ordered when the display is manufactured, so in the event of a replacement, the replacement panels are as close as they can be to the original display. Some of the manufacturers have acknowledged this, and have color correction built into the controller software. Not all controllers have this option, so keeping spare panels is most likely the best option.
Best uses
Digital signage works best when the content is kept simple. There are certain tips that can make a display look its best. You should always try to use large bold font, and use as much real estate of the display as you can. Avoid, drop shadows, fancy font faces, italics, white backgrounds, and close contrasting colors. When using images, avoid color gradients, and small images. Lastly, avoid transitions, simple cuts between messages looks the best. You only have a few seconds to get your message across, do not waste seconds with animations. Try putting a custom message on the display and see what looks best, and do not to leave the default time/weather cycle on your display, as it looks like a VCR from the 80’s flashing 12 o’clock.
What should you ask when shopping for an LED display? Be cautious of demanding a specific specification. The goal here is to define what your requirements and expectations. Then have a sign company give you a quote, and ask for multiple configurations. Let them do the design, and look it over to see what they offer. Then use that as a starting point. What pixel composition and pixel pitch did they propose? Was there any discussion about software, and spare parts for maintenance?
We have seen better quality screens “look” worse because of the way the content was presented. We have also seen poorer displays look pretty great because the content was formatted in a way that did not exceed the capabilities of the display. Chinese competitors have become good enough sometimes. Most people may not recognize the flaws, and accept the limited software for displaying text and configuration the display. Understanding these tradeoffs, and using the screen to your full advantage is important. Other times, expectations vs. reality can lead to regret.
