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Understanding Your LED Signage Quote

Understanding Your LED Signage Quote

LED Signage Manufacturing Standardizations and Regulations

The LED signage manufacturing industry is to a large degree lacking standardizations and regulations. From an industry perspective, standards and regulations provide a platform for consistent and uniform language, particularly in regards to definitions, test methods, product design, specifications, and manufacturing. The outcome of such deficit is that different companies use different terms and specifications when selling their product. This results in even expert sign shop owners sometimes getting confused. As an example, a manufacturer claims to be selling a 4 x 10 foot LED Sign with a 10mm virtual pixel pitch while their competitor promises that their 3 X 9 foot 19mm true pixel pitch LED display is equal, if not superior, to the aforementioned product and a third firm declares that their 19.25mm pixel pitch LED board has the highest resolution of the three. Who is actually delivering the best product? This article is an attempt to clarify the information typically presented. It hopefully will clear up most of the confusion associated with understanding LED Signs quotes.

No Borders For The LED Boards

Most antiquated LED panel manufacturers pre-build their signs “Cabinet Style” at their factories and then ship the whole LED display as one single unit to their customers. The cabinet itself (see picture to the left) encases the LED modules within a box. When such manufacturers quote their products the dimensions they take into account are the ones of the LED cabinet around the sign, including the border edge, which normally add as much as one Foot of width and one Foot of height. Years of research has proven that LED cabinet style signs waste power and have a higher rate of system failures. These enclosed structures use large power supplies that consume -and waste- great amounts of electricity, in the process of generating considerable heat. Interior fans -known to be prone to failure- need to be placed to cool the system off. Fans suck outside air filled with moisture and dirt, depositing contaminants onto the delicate electrical components. At the same time, each fan requires a significant amount of power to run, increasing the temperature inside the cabinet. Moreover, the cables spread out across the board waste electricity as currents pass through the display, a process known as “resistive heating”. All this means a simple fan outage could cause terrible damage to the LED boards. If the LED display fails, a new LED sign cabinet will have to be assembled in the manufacturer’s factory and shipped back for re-installation. For these reasons, pioneering LED panel manufactures do not encase their LED boards in a cabinet. Some, such as Cirrus LED Systems, manufacture slim, lightweight LED tiles with a completely sealed, waterproof module built with naturally cooling materials. That way, the panels itself consume very little energy, not only lowering the sign owner’s electric bill, but reducing the overall heat and nullifying the need for fans. The LED tiles can be assembled on-site by interlocking the panels; there is no need for a cabinet. And, in the off-shoot case that an LED tile has a problem, it can easily be switched by a new one without needing to ship the whole digital sign back to the manufacturer. These all seem like advantages at the time of purchasing a sign. Still, when the pioneering LED manufacturer has to quote their digital display, without the added extra width and length of the cabinet, the LED sign is going to appear one foot shorter and one foot slimmer to the uneducated customer. The lack of an industry standard allows some manufacturers to quote several feet of frame as part of their sign, making ten feet of cabinet really a nine foot sign. And in times when the space for signage is constrained, one foot of cabinet is most likely stripping the owner of one foot of LED panels.

LED Pixels: The Truth Behind The Pitch

LED display systems are usually quoted with pitch as the defining specification for resolution. The lower the pitch, the higher the resolution. Or so we have been made believe. Traditionally, pixel pitch measured the distance from the center of an LED cluster (or pixel) to the center of the next LED cluster/pixel in millimeters. However, now, many LED display manufacturers -mainly LED companies from China- have taken advantage of the lack of industry standards to offer a new pixel configuration and quote what they call “Virtual Pixels”; claiming that “Virtual Pixels” double the actual resolution of the screen, i.e a 20mm pixel pitch LED screen would have a 10mm virtual pixel pitch. In the traditional true pixel configuration, each pixel consists of one red, one blue, and one green LED diode. However, a virtual pixel LED screen uses two lower output red LED lights per pixel to work as one; in a virtual pixel LED panel, each pixel consists of two red, one blue and one green LED diode ordered in a square matrix. This, in our experience, is more of a fail-safe design decision than a higher pitch resolution commitment on behalf of these LED panel manufacturers; red lights tend to age more quickly and a double red diode allows this fabricators to use lower quality materials and still be able to sell a sign that will function for the duration of their warranty. In a virtual pixel configuration, since red LED lights are more likely to fail, they are set to display at fifty percent of the power, that means that over time, red LED diodes fade at a slower rate than the blue or green LED diodes, which more often than not gives the LED sign a pinkish tinge after it has been on for as little as six months. However, the virtual pixel LED board manufacturers claim that this configuration allows each LED diode to be “shared” by the contiguous four pixels. Therefore, when counting pixels, the first four diodes grouped together are counted as the first pixel. Then the third, fourth, fifth and sixth form the second pixel. After that, the fifth and sixth diodes are combined with seventh and eighth and grouped as a third pixel, and so on. In a traditional true pixel matrix each LED diode gets counted as part of one pixel, in a virtual pixel matrix it gets counted as part of four virtual pixels. And it stands to reason that each LED diode can produce one level of brightness, not four. According to Screen Magazine, “In a “virtual pixel” mode one screen pixel contains information on four pixels of the initial image. The image projected on a screen has doubled resolution in each dimension compared to a “physical” resolution of a video screen. This usually leads people to conclude that screen resolution also doubles. Which is not exactly true. In fact, one screen pixel cannot hold and display all information from the initial four pixels. Part of the information gets lost. The result may be the following: Let’s say that the displayed image (with resolution twice as high as a “physical” screen pixel resolution) displays a horizontal green line (one pixel thick) on a black background. If the line appears on an even row of pixels, the video screen will display a corresponding green line. But if the line shifts to an odd row of pixels, it will simply disappear: the video screen will remain black. In other words, smaller details and sharp color borders shall be displayed with distortions which are not evident in an initial image.” In reality, at very close distance, a virtual pixel sign might look crispier but at farther distances, the lack of black space between pixels does not allow for enough contrast and the image gets blurrier. Considering that most people purchase LED signs to attract attention at a significant distance, it is not close proximity viewability that they have in mind when they are looking for a LED message center or digital billboard. Furthermore, to avoid distortions that were not corrected by the designers during the image adaptation, “virtual pixel” LED boards frequently operate on standard “true pixel” mode with one of the red LED lights turned off. In the end, one has to wonder why all the higher end brands steered away from this configuration and only manufacture true pixel LED boards. Nevertheless, when determining pixel pitch virtual configuration LED sign manufacturers take advantage of the way they count each pixel to measure the pixel pitch by calculating the distance between one LED diode and the next -instead of between the center of two RGB true pixels- that way, a 20mm pixel pitch becomes a 10mm virtual pixel pitch, making this approach more about sales and marketing than providing a quality product.

The pixels on the LED sign round up and down, all through the town

Another thing that normally gets overlooked when reading a quote is the rounding of the decimals in the pixel pitch. Some LED board manufacturers will round the pitch to the nearest whole number, so if their pitch is 15.6 mm, it will be quoted as a 16 mm pixel pitch LED panel. Yet, many LED manufacturing companies, again taking advantage of the lack of industry standards, will always round down. What does that mean? That a 15.6 mm -or a 15.93 mm- will be offered as a 15 mm pixel pitch LED board. At first look, this might appear inconsequential, but it’s not. On a smaller LED display, the 0.93 mm difference in pitch will not have a huge impact on image quality, or price. However, in larger displays -such as a sizable LED digital billboard, or a larger Electronic Message Center- where a sign shop needs to make sure that the end-customer gets the best results, a 0.93 mm difference in pitch will have a huge impact on the resolution as that 0.93 mm differential expands exponentially. Back to our initial example of a four by ten feet -or forty square feet- LED sign with a 19 mm pixel pitch, if the first LED manufacturer’s quote is for a 19 mm pixel pitch, that equals 257 pixels per square feet ( (1000/19^2)/10.764 or the square of one meter divided by the pixel pitch in millimeters and multiplied by the amount of square feet in one square meter) and 10,294 pixels in the forty square feet LED digital display. By contrast, if the quote is for a 19.93 mm pixel pitch that would equal 234 pixels per square feet and 9,356 pixels for the complete LED sign. That is a difference of 938 pixels; over four square feet of LED panels! So, when comparing quotes from different LED board manufacturers it is important to always check the exact pixel count of their board or their price per pixel.

Summary

In summary, the lack of standardization and the “creativity” of some LED panels manufacturer’s marketing departments make comparing quotes for LED signs a complex job that requires understanding of the diverse terms used by the different companies. We hope this article has helped clarify some of the misconceptions and paint a clear picture of what to look for when you are bidding your next project. Other factors, not discussed in this article, but also important to keep in mind when comparing LED products are: The power consumption of the sign; greener signs are more efficient and consume less power which increases their lifespan and reduce maintenance cost, to learn more about this read our “Go green” guide . Another key factor is programming software, the easier it is to create appealing messages for billboards and electronic message centers, the more flexible and effective the LED signs are going to be, read our “LED Signs: The Most Effective and Least Expensive Form of Advertising” article and find out more about our Cirrus LED Cloud Software. Download the pdf version of this article.
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