What are louvers and why are they in front of your screen? These often overlooked components are critical to a good image
By Joshua Echo-Hawk
Contrast is a very important factor when comparing the quality of manufacturing in a video display. Contrast is essentially the difference between brightest white from the blackness of the screen when power but no color is applied to the display.
There is a focus in consumer televisions to achieve true black-- and there is good reason for this. The current-day LED diode is made of up a combo of red, green, and blue pixels. This accomplishes an outstanding array of colors-- except for one of the most important colors of all, black.
Contrast is essentially the measurement of light against dark-- and the darker a screen can display, the better the image. However, not everything in contrast is derived from the light emitting diodes.
A very large factor in blackness of a display is the actual plastic that houses the LEDs. The blacker the the plastic is behind the LED diodes, the better imagery is going to show up in the daytime.
With a blacker background, the images can pop more vividly because the eye isn't seeing a gray plastic background, we just see the bright image of the display. Additionally, this allows the screen to run more efficiently-- drawing less power. This is especially helpful in daylight so the light emitted from the LEDs does better when competing with the sun.
This allows for a better image, and a more efficient display.
LED diodes live in a housing of plastic. This plastic holds the diodes together in a pattern, and ensures the LEDs are protected from moisture, weather, etc. One of the most important pieces in the design of the housing is the ridges that shade each diode row, commonly known as louvers.
Between the rows of pixels, we should not see the plastic louvers. It should be black or invisible. There is less plastic between the pixels in a higher resolution screen, so when there is a tighter pixel pitch in a higher resolution screen, there is less black plastic between pixels-- but there is still plastic there, and it should be very black and very consistent in color.
Plastic reflects. There's no way around that. And almost every installation of a display will come with sunlight, spotlights, ambient light, or some other light that will want to reflect off of the plastic in between each pixel.The design and manufacturing of louvers is extremely important to channeling light into the viewers eye.
A thick, rounded, or poorly manufactured louver will result in the light from the sun or stadium light bouncing off the plastic and back into the viewers eye-- essentially competing with the light from the sign.
In low-cost overseas models, there can be a significant amount of gray reflection in a display.
This will cause a major problem in the contrast of a display. The display will appear washed-out instead of vivid and crisp.
Over time, there are two critical factors (that have nothing to do with the actual LEDS) that can deteriorate the picture quality of a display:
Obviously, signs will become dirty, worn, or stained. This dirt rests on the plastic of the housing and can essentially bake in to the display. This can cause the plastic of the display to become faded, gray, and lighter in color. This dirt dramatically increases the gray factor in the plastic and harms the contrast of a sign, making it dimmer.
While pressure washing a display can greatly help-- and should be done regularly, the quality of plastic is critical to not absorb dirt, or fade over time.
The bottom line is that cheap plastic fades in the sun. Consider the automobile industry, and how we see the sun affects plastic components. The sign business has the same problem, and the quality of plastic used in a display is absolutely critical to keeping that display looking good over its lifespan.
Another key factor in quality of manufacturing is the thickness of louvers. The higher end manufacturers strive for a very thin edged louver. It should be as razor thin as possible, shade the LED diode, and be made of a plastic as black as possible to cut down on ambient reflections.
Cheap manufacturers will simply not deliver as high a quality of louver, and that will impact the contrast and overall picture quality of the display.