The electronic message centre (EMC) occupies a somewhat contradictory position within the sign industry. The concept of a changeable sign with some electric components has been around for about 80 years now, yet it may also seem to many sign shops like outdoor electronic displays are a new, untested technology.
It is nearly impossible to drive through any Canadian city today without seeing EMCs as an important part of the signage mix, for example, but there are still many sign companies that have either (a) never sold an EMC or (b) sold a few but do not consider them an essential or even important part of their product offerings. The reasons for this contradiction include a combination of customer interest levels, the perceived high cost of the initial investment in an EMC, local sign ordinances’ allowance for this technology and, of course, the degree to which a given sign shop is interested in and comfortable with EMCs.
While the recent widespread adoption of EMCs could be perceived as bad news for the ‘traditional’ sign industry, it actually represents a growing opportunity for those signmakers who are interested in actively selling EMCs themselves but have not yet taken the leap into this product category.
Choosing a manufacturer
That said, given today’s wide variety of manufacturers of outdoor electronic displays around the world, the decision to enter the EMC market can be a complicated one, as there are too many different brands to offer to a sign shop’s customers. It is advisable to keep the following factors in mind:
Maturity in the industry—For how many years has a given manufacturer been specializing in building EMCs? A relatively small number of these companies have been in business for more than 10 years—and only a handful have been manufacturing displays for more than 30 years. As in any industry, choosing a ‘mature’ supplier with a strong track record can help ensure the best mix of value, robust technology and long-term customer satisfaction.
Ease of access—The ability to meet and talk face-to-face with a manufacturer’s factory representative should never be undervalued. This person will be needed not only to support the sign shop with work in the field, but also to help both the shop and its customers if any problems arise after the sale.
Demo support—Is there a demo unit to be placed in front of the customer? The purchase of an EMC is somewhat analogous to the purchase of a vehicle, in terms of cost and the important of making the right decision. Hence, allowing the customer an opportunity to ‘test drive’ an EMC before purchasing it should be a basic step in the sales process. It will both educate and reassure the customer.
Software support—In addition to robust hardware, has the EMC manufacturer developed good software for controlling the sign? It is important to check and not simply assume the best. The customer will buy the hardware once, but live with the software every day, so that software needs to be intuitive and easy-to-use.
Power consumption—Even in an age of ever ‘greener’ and more sustainable technologies, buyers need to be aware of power consumption, as some brands of EMCs will use twice as much electricity as other, more efficient models.
Sales structure—Another aspect of the manufacturer to look into is whether or not it is a direct competitor to the sign shop. Many EMC manufacturers sell both to signmakers and to those signmakers’ customer base. A few, however, concentrate more on developing long-term relationships with individual sign companies as their authorized dealers, keeping out of the direct-to-user market.
When entering the EMC market for the first time, a sign company will need to understand the unique terminology of the industry and be able to explain it to potential customers during the sales process. Some of these terms will be key to finding the best match between a customer’s needs and what is available.
In an age when high-definition television (HDTV) has become ubiquitous, for example, new customers may well have a skewed notion as to how sharp the resolution of an outdoor display will need to be to produce a clear image. Even the most technologically advanced EMCs, however, are very low-resolution displays compared to consumer devices used inside the home. This is because all large outdoor displays use individual (often referred to as ‘discrete’) LEDs to convey full-colour photographic and video content. Generally, the arrangement of each ‘pixel’ within the display comprises one each of red, green and blue (RGB) LEDs. These pixels are the building blocks of the EMC.
The pixels are arranged in a matrix, the scale of which determines the EMC’s total resolution and dictates the maximum size and sharpness of the displayed ../images. So, rather than measuring the physical size of a display in metres or feet, an EMC is generally measured in terms of pixels. A 48 x 96 matrix, for example, offers a resolution of 4,608 pixels. The higher the total pixel count, the better the image quality.
像素以矩阵排列，其比例决定电子导视牌的总分辨率，并决定显示图像的最大尺寸和清晰度。 因此，不是以米或英尺来衡量显示器的物理尺寸，而是通常以像素来衡量。例如，48 x 96的矩阵提供4,608像素的分辨率。总像素数越高，图像质量越好。
The distance between pixels (known as ‘pitch’) also determines the clarity of the display—i.e. the closer the pixels are placed in proximity of each other, the more detailed the graphic content can be. It is common to see pixel pitches as low as 10 mm (0.4 in.) for outdoor displays today, although the industry’s current ‘bread and butter’ is in the range of 16 to 20 mm (0.6 to 0.8 in.).
The aforementioned 48 x 96-pixel matrix display, for example, with a 20-mm pitch would offer an active display area of about 0.9 x 1.8 m (3 x 6 ft). Within that same area, however, if the display were instead designed with a 10-mm pitch, the matrix could reach at least 80 x 160 pixels, for a total resolution of 12,800 instead of 4,608.
例如，前述的48×96像素矩阵显示器，具有20毫米的间距，能提供约0.9×1.8米（3×6英尺）的有效显示区域。但是，在同一区域内，如果显示器的设计间距为10毫米，矩阵可能至少能达到80 x 160的像素，总分辨率能达到12,800。
While a lower pixel pitch would therefore seem to promise a better appearance for a given image on a given display, this level of effectiveness depends on the EMC being seen by an audience beyond the minimum effective viewing distance (MEVD) of its given pitch.
Indeed, there are some guidelines to help a customer understand and choose which pixel pitch will be appropriate based on the sign’s size and location. With a closer viewing distance, a tighter pixel pitch will usually be required to ensure people see the ../images or graphics clearly.
The general ‘rule of thumb’ is to multiply the pixel pitch (in millimetres) by five to determine the MEVD (in feet) for people to stand away from the display to see ../images clearly. With a 16-mm pitch, for example, the MEVD would be 24 m (80 ft).
If an EMC is to be installed considerably high up—e.g. 12 m (40 ft) in the air—and/or well back from a roadside, the sign shop could opt for a less ‘dense’ display, as a 20-mm pixel pitch will probably be more than sufficient. If it will be installed only 3 m (10 ft) in the air, then a 12- or 16-mm pitch might be a better choice. And if it will be mounted in a parking lot where drivers will pass by closely, a 10-mm pixel pitch would be appropriate.
The next concept for the customer to understand is the viewing angle. Generally, an EMC has a horizontal viewing angle of 140 degrees and a vertical viewing angle of 70 degrees. Within the viewing area defined by these angles, the ../images will be seen clearly and the screen’s brightness will be 100 per cent.
The brightness of EMCs is typically measured in terms of luminance, in candelas per square metre (cd/m2), also known as nits. Generally, monochrome EMCs provide lower luminance—in the range of 4,500 to 6,000 cd/m2—than full-colour EMCs—7,500 to 1,000 cd/m2.
电子导视牌的亮度通常以坎德拉每平方米（cd / m2）表示，也称为尼特。通常，单色电子导视牌可提供较低的亮度，范围为4,500至6,000 cd / m2，全彩色电子导视牌的范围为7,500至1,000 cd / m2。
It is very important to pay attention to luminance when selecting an EMC because the quantity of light it emits will decrease by approximately nine to 17 per cent after the first year (or roughly 10,000 hours) of operation and gradually after that. Eventually, it will tend to even off at about 50 per cent of its original total brightness after 100,000 hours of use.
Discrete and SMD models
There are also multiple types of EMCs on the market today, including discrete and surface-mounted diode (SMD) variations. It is relatively easy to identify a discrete display because, as mentioned earlier, it is a matrix made up of individual LEDs. In an SMD display, on the other hand, each set of RGB LEDs is contained within a package called a ‘chip.’
For the majority of EMCs on the market, discrete LEDs have been the dominant technology, at least until very recently. SMD displays have been available for indoor use for quite some time, but only now are being commonly adopted for outdoor installations, as well.
The choice between these two options will depend on the prioritization of the factors mentioned earlier. SMD displays offer a much wider viewing angle and comparatively lower cost, for example, but are not as bright as discrete displays. The lower light power output of SMD displays is due to the smaller size of the overall chip. That said, great strides have been made in increasing the brightness of these displays in the past few years, which is helping drive their use in outdoor applications.