By Jef White

As LEDs gain in popularity, there are many differences between them and traditional neon and fluorescent options.

Color matching, however, isn’t necessarily one of them.

As sign shops work with their customers to get just the right color for a channel letter set or other lighted sign, they can do so knowing that lighting them with LEDs won’t present a batch of unique challenges to be overcome.

“From a sign OEM side, when it comes to matching colors, the comforting part is that the tools and tricks they use now with neon, they are going to he able to use those same tools and tricks with LEDs,” says Jeff Nail, technology segment manager, signage, for GE Lumination, Valley View, Ohio. “There’s no magic to the LED color versus a neon color. It’s the same challenges the sign OEMs had before with neon.”

In fact, sign makers can use the physics of LEDs to offer specific colors that stay constant over time, knowing that colored LEDs arc producing light only within certain wavelengths. Meanwhile, for harder-to-achieve colors, white LEDs behind vinyl or acrylic faces can do the trick.

Improving LED and sign face technology is creating more quality options for a variety of colored signs, and LED manufacturers can offer help when a color combination just won’t seem to come together any other way.

THE PHYSICS OF LEDS
When using colored LEDs to light a channel letter or cabinet, sign makers know exactly what color they will get with the LEDs they choose.

“LEDs can only be manufactured to produce light within certain wavelengths,” explains Gary E. Maag, general manager, CAO Group, West Jordan, Utah. “Colored LEDs are monochromatic. In other words, they can emit only one wavelength of light.”

Therefore, sign makers can achieve just the color they are looking for, he says, if they read and understand the typical wavelength of the desired LED, and choose a vinyl to match.”

Jordon Papanier, marketing manager for LEDtronics, Torrance, Calif., notes that color rendering index (CRI) matching is made easy “because color LEDs arc nanometer-specific. You have to know the color of the material that you want to light up, and match that with the LED light.

“You want to use the same LED light color as the lens or face of the sign that you are backlighting,” he continues. “'If you have a channel letter with a red face, then you want to use red LEDs. Note there are a few different nanometer red LEDs on the market, as with just about any othcr LED color, so you may need a few samples of the LED to test with your sign to see what matches up the best.”

Consistent wavelengths mean the color a sign starts out as is the same color it will be producing years later.

“Color consistency is very good. For the colors, especially for the saturated red or blue or green, that LED does not change wavelength over time. Its face remains the same color,” says Nall. “The nice thing with LED is that you can get efficiencies because, with red, for example, if it is 625nm (wavelength), all that 625nm will come through the face and look very clean and bright.”

Those wavelength parameters, however, can affect how colors look from day to night, based on the type of face material used.

“Depending on the wavelength filtering of the face, what you’ll see is the LED color rather than the whole range of integrated wavelengths of what the face is really filtering,” says Nall. “If you picked a red-orange-type of face (for the day), you’re still going to get the same look of red at night as if you had just a red face.”

Maag uses a more extreme example, where if blue LEDs are used behind a red acrylic face, no light would be able to escape.

“We have all seen examples of this, when a customer chooses a specific vinyl logo color that is the true color during the day, but a different color at night when lit with LEDs,” he says. “The only color getting through the vinyl is the selected wave1ength of the LED.”

Because of this, he notes, sign shops will want to populate a sign with a single LED manufacturer’s product to ensure consistency.

“Do not mix-and-match LED brands,” he says. “Every company has a different specification for typical wavelength. The difference in color may only be a few nanometers, but if various LEDs are used, there will be dramatic, undesirable results.”

Those wavelength parameters may also lead shops to encourage their customers to go with common colors when choosing a sign.

“Where we’ve seen very good success is where customers have a red sign or a standard blue or green sign,” says Nall. “It will be less expensive for a saturated color versus white.”

“The sign shop can help the customer with a more economical choice by helping to choose a logo color with a common wavelength,” Maag adds.

THE WHITE CHOICE
Of course, not everyone will want to go with a typical color. That’s where white LEDs come into play.

“When you get into tough colors like purple, brown or pink—something that’s really a mix of different primary colors, so to speak—that’s when you’d fall back on using a white LED to backlight them,” says Nall. “Where you get into color-mixing, like with a teal blue or light blue versus dark blue or royal blue, you essentially don’t have the ability to tailor the color, so it becomes a white LED solution.”

“If the customer demands a certain off-color, then white is the all-forgiving LED choice,” Maag says. “White LEDs emit all colors in the spectrum. If a sign is made with a vinyl coating that has several colors, or a color with a very rare wavelength spectrum, then white LEDs are the best choice, because all of the colors will shine through the vinyl.”

That can make matching a specific color a bit tougher, however.

“CRI matching is most difficult when using white LEDs,” notes Papanier.

The suppliers say that white LEDs have come into their own versus other popular color choices such as red, thanks to decreases in price and increases in brightness.

“The good thing is, every day white LED gets better,” Nall says, noting GE recently launched its latest Power White product line that offers 65 lumens per watt. “They are much more efficient, offer a much higher light output now, and that makes the white LEDs more competitive in look and efficiency. Also, as white LEDs get brighter, it make it easier to color match, because now you have the punch to really get the color you want.”

That offers a wider color palette, he explains, meaning they can light up more of the base colors that represent mixes of primary colors.

“As the white LEDs get brighter, it allows the sign OEMs to be more cost-effective, because the amount of light we are able to get out in the individual modules allow us to penetrate through the faces to get to some of the deeper, darker-colored vinyl, which makes it more cost-effective,” he says.

Stronger whites also mean fewer LEDs populating a sign, again decreasing costs. The module manufacturers note that the number of LEDs in a particular sign doesn’t necessarily affect its color, but of course changes the intensity.

Hot spots where the specific LED light source can be seen through the sign face, a well as dark or cold spots where there is not enough light, are also factors. Painting the inside of the channel letters white can help light bounce around more inside and better diffuse the light output, and newer plastics are also making for a more uniform, balanced appearance.

“That’s also a reason for using white for some of the special colors,” Nall says, “is that it’s very consistent.”

Papanier can also see possible pluses for future sign designs.

“Maybe as the LEDs get brighter the sign will get lighter and thinner, saving weight and valuable natural resources,” he says.

PROOF IN THE VIEWING
The proof of an attractive, color-matched sign lit with white or colored LEDs is in the viewing.

The module manufacturers say sign shops shouldn’t he afraid to show customers what a sign will look like illuminated after dark, and be prepared to offer a couple of color choices in appropriate instances.

“It’s relatively simple to pick a color that you want during the daytime. But, before presenting it to a customer, it may be helpful to have a couple of different options for the nighttime look,” Nall says. “It is sometimes difficult to just view the daytime look and really understand what it will look like at night. There is a color difference, and the only way to really see it is to light it up and see it at night.”

That’s particularly true when using some of the newer face material that may offer unfamiliar transmissivity and diffusivity properties.

“Advances in acrylics and vinyl made esspecially for LEDs are starting to hit the market,” Maag notes. “They allow a richer spectrum to be seen, and are brighter at night.”

LEDtronics’ Papanier adds that experience working with LED lighting systems will help sign makers determine their quality and longevity.

“Use stable-quality LEDs or LED sign products,” he says. “Some LEDs and products will degrade faster than others. The light level may drop as much as 40 percent in the first 90 days. As light drops, the light color will shift and the CRI that you started out with could be much different. Remember the old saying, ‘You get what you pay for.’ ”

The LED suppliers say they are also available to provide assistance when needed.

“If there is a very specific color that the sign OEM is trying to find for his customer, GE can help,” Nall says. “We have spectrometers and transmissivity measurement devices that allow us to determine what the wavelengths are on the face material, and also measure the color point on the face using LEDs to do some of that matching.”

“A good sign shop distributor can assist with many details such as LED, acrylic and vinyl election,” says CAO Group’s Maag. “In addition, a good LED manufacturer will offer design services such as product layout suggestions and color balancing.”

Assuring you’ll get the hue that is all you.