LED screens offer many advantages over LCD screens and sometimes these advantages come at a steep cost. The most critical factor in determining the cost of an LED screen is the number of light-emitting-diodes the screen contains.
Obviously, a larger screen has more light-emitting-diodes and is more expensive than a smaller screen. But two screens the same physical size can have drastically different price tags due to the number of light-emitting-diodes the screen contains. The density of the light-emitting-diodes in an LED screen is referred to as pixel pitch.
LED Pixel Pitch
One set of red, green and blue light-emitting-diodes (LEDs) make up a pixel. Numerous pixels combine together to create the "picture" displayed on the screen. The space between each pixel, or each set of light-emitting-diodes, determines how detailed the content appears on the screen.
Screens with a higher pixel pitch have more distance between each pixel, or each set of light-emitting-diodes. More distance between each pixel means more space must be illuminated by one set of light-emitting-diodes. When the space between the pixels is too great, the color created by each set of light-emitting-diodes becomes detectable to the human eye.
Some graphics appear pixelated when displayed on an LED screen with a higher pixel pitch. A screen with a lower pixel pitch usually provides more detailed graphics, better-defined edges within the graphics and improved visual quality.
However, at greater distances, a lower pixel pitch does not always provide a visual improvement. Many factors determine the right pixel pitch to select for each screen, but two of the most important are: viewing distance and content.
Pixel Pitch & Viewing Distance
Viewing distance refers to how far from the video wall screen the average viewer will be. The LED market has developed many formulas to determine the best pixel pitch for a given scenario. A common approach is the 10x Rule:
Approximate Viewing Distance in Feet = Pixel Pitch x 10
The formula states the pixel pitch of a screen in millimeters should be about 1/10th of the distance viewers are located from the screen. This is a simple method to determine the best pixel pitch based on the Visual Acuity Distance test.
If viewers will be approximately 50 feet from the screen, a pixel pitch of 5.00mm is recommended. If viewers will be 25 feet from the screen, a lower pixel pitch of 2.25mm is recommended. If viewers will be able to touch the screen, a pixel pitch of 0.6mm or less is recommended. In conclusion, selecting a lower pixel pitch provides an improved experience up to a certain distance, at which the more expensive, lower pixel pitch may not be worth the investment.
Pixel Pitch & Content
The type of content that will be displayed on the screen can also play a role in determining what pixel pitch is required. A lower pixel pitch is required for detailed imagery while simpler graphics, like text, may not benefit from the investment of a lower pixel pitch.
Best Practices for LED Content
Developing content for a video wall requires special consideration. As always, resolution and correctly-sized media is a critical factor in achieving great-looking digital signage! LED video walls require some additional consideration regarding text and colors.
Resolution
Resolution is the numbers of pixels a screen can display in each direction. Graphics should typically be designed the same size as the resolution of the screen, or slightly larger. Graphics that are smaller than the resolution of the screen appear pixelated.
However, it is a know practice for LED content designers to use graphics that are much larger than the resolution of the LED screen. Light from each pixel, or each set of light-emitting-diodes, can blend into the empty spaces between pixels and depict additional color information to the human eye.
Text
Keep messages comprised of text short and simple. Video walls are often placed in busy locations where many distractions compete for viewers' attention. Short messages are more likely to be received and processed before the viewers' attention is diverted. Long messages look crowded, require a smaller font and are not legible at greater distances.
If a lengthy message is required, it is recommended to spread the message over multiple frames.
A helpful minimum is to choose a font size that is one-fourth of the screen or larger.
A font with thick, solid strokes is mandatory. Thin fonts and fonts with detailed letters are much harder to read at a distance. Colored text benefits from a black outline around the letters, providing extra definition against background colors.
Colors
It is recommended to avoid large areas of pure-white (255, 255, 255) on an LED screen, such as the background color. To produce pure-white color, all three red, green and blue light-emitting-diodes must illuminate at their maximum brightness. Any other content on the screen often dwindles in comparison to this brightness.
Secondly, LED screens should not display a pure-white, pure-red (255, 0, 0), pure-green (0, 255, 0) or pure-blue (0, 0, 255) color for an extended period of time. The excessive current it takes to produce pure-colored light can be damaging to the light-emitting-diodes and reduce the lifespan of the screen. It is preferred to display dynamic content, or content that has constant movement, and to use blended colors instead of pure.
For any video wall, it is essential to have high color contrast between text and the background. Messages can easily be lost when the text and background colors are too similar, as illustrated in the images below.