LED has now become the standard illumination media for channel letter signage. However the proper use of LEDs (and matching them correctly with other channel letter components) can make the difference between a mediocre letter set and an excellent one.
This article will outline some of the common issues and solutions relating to the usage of LED channel letter illumination.
LEDs and Color Considerations
LED illumination is available in a variety of colors. White is the most common, but other colors may be utilized to generate the optimal illuminated letter appearance.
For example, one potential configuration is to simply match the LED color with the face acrylic color. This configuration will often result in a stronger color appearance. For example, red LED modules can be matched with red face acrylic.
However this layout also has some limitations.
Red LED emits a color with a narrow bandwidth. If the color bandwidth of the face acrylic does not match the LED color bandwidth, then some of the colored illumination will not be transmitted—instead it will be absorbed.
Nonetheless a color match between the LED and the letter face acrylic will often yield a more compelling and colorful illuminated channel letter appearance.
For example, compare Photo A (a logo box with a sub-return in the center lit by red LEDs) with Photo B (the same logo box lit by white LEDs).
The cost of the sign is another consideration. While a channel letter sign that has a matched LED and face color may have an improved illuminated appearance, it will also usually have a higher price. Colored LED is typically more expensive than standard white.
So the potentially improved letter appearance from an LED/acrylic color match must be weighed against the higher cost. However many customers find the higher price is well worth it.
LEDs and Viewing Angle
One important LED feature affects both the necessary stroke quantity and the mounting distance between modules. That feature is called the “viewing angle” (Photo C), and the specified angle varies among differing LED brands.
The viewing angle tells you the distance covered by the “fan of light” produced by a module prior to losing half of its peak illumination level. The angle is simply a measure of the position where the intensity of the LED light spread reaches 50 percent of its maximum brightness.
A professional-looking channel letter will have the faces lit evenly and consistently. Using an LED with an inadequate viewing angle (for the amount of installed LEDs) may cause a common channel letter illumination problem: a letter face area that appears brighter than the adjacent face area. This is sometimes referred to as “tiger striping,” and it detracts from the illuminated appearance of a channel letter sign.
One related cause of this uneven face illumination is the number of LED strokes that have been placed within the letters.
A “stroke” is simply a strand of linked LED modules mounted within a letter interior. For example, Photo D shows a channel letter return with a single-mounted LED stroke. Photo E shows a double-mounted LED stroke.
If too much space is placed between the LED strokes (after the module viewing angle has been taken into account), then the illuminated letters will exhibit uneven face illumination.
The main point is this: The illumination viewing angle emitted by each LED module impacts both the number of strokes necessary to clearly light a channel letter sign and also the correct mounting distance between the strokes. The letters may have uneven illumination, if too much space is placed between the strokes.
LEDs and Energy Consumption
Another consideration in LED illumination is the wattage used per module.
Each module within an LED stroke requires a specific amount of wattage for operation. This watt usage difference can add up over time, especially in terms of power consumption.
For example, some LED brands utilize as little as 0.24 watts per module, while others use as much as 1.5 watts.Multiply that number by the quantity of modules contained in the entire sign and you have that sign’s ongoing wattage consumption.
The optimal approach is to utilize the lowest LED wattage necessary to brightly light your customer’s channel letter sign. That amount gives your customer the best of both worlds—bright illumination and lower utility bills.
LEDs and Module Brightness
LED module brightness (illumination intensity) is measured in lumens. All things being equal, a higher number of lumens per module results in brighter letter illumination.
LED manufacturers will typically state a brightness measurement in both lumens per module and lumens per foot.
For example, one producer is currently listing a channel letter LED product that produces 130 lumens per module and 195 lumens per foot. That also means this product has 1.5 LED modules per foot (130 lumens x 1.5 = 195 lumens).
An important trend taking place in the LED industry is that individual LED modules are now generating a higher number of lumens than in the past. In turn, that means fewer modules per channel letter may be used to produce the same level of face illumination.
This is a significant development for several reasons.
First fewer modules mounted within a channel letter sign could mean a lower energy bill for your customer.
Second greater illumination levels from individual modules means a decreased risk of uneven face illumination.
Lastly this also means that smaller channel areas (such as the tip of a serif letter font) may now receive an increased level of illumination.
In the past, a tight corner of a channel letter could mean dimmer illumination of that face area because the smaller mounting space restricted the placement of additional LED modules. The increased illumination output of this newer LED generation decreases the risk of that problem.
LEDs and “Hot Spots”
One potential channel letter illumination issue is something commonly called a “hot spot.”
A hot spot is an illuminated LED module that is physically visible through the translucent acrylic sign face. (Note: The term “hot spot” is also sometimes used for the previously mentioned issue of uneven face illumination.) LED module visibility is an unsightly condition that detracts from the professional appearance of an illuminated letter set.
The depth of the letter return may contribute to the possibility of hot spots.
Hot spots are typically treated in two ways.
First the interior of the letter cans may be coated with reflective white paint. The reflective surface helps to evenly distribute the LED illumination through the letter interior and decrease the “hot spot” appearance.
A second method is the use of a product called diffuser film (also known as light management film.) This product is mounted to the interior of the letter face acrylic and distributes the LED illumination more evenly.
By John Baylis, marketing director at Direct Sign Wholesale in Denver, Colorado.
Photos: Direct Sign Wholesale.
