LED Academy
Everything about LED display technology, clearly explained. Each article at three levels: for everyone, student or expert. You choose how deep you go.
Light
Brightness and nits: how do you measure the light output of an LED screen?
‘Nits’ is the unit that tells you how bright a screen is. But what exactly does that mean, and why does an outdoor screen need thousands of them while an indoor one needs far fewer? A clear explanation of how light is measured.
The electromagnetic spectrum: where visible light comes from
The light an LED screen emits is a form of electromagnetic radiation, just like radio waves or X-rays. Yet our eyes see only a wafer-thin slice of that whole spectrum. Here you will discover which slice, and why.
Wavelength and frequency: how light gets its colour
Colour is no accident: every colour of light belongs to a specific wavelength. That explains why we can describe an LED colour precisely in nanometres, and why our eye perceives one colour as much brighter than another.
Measuring light: radiometry and photometry
How ‘strong’ is light? There are two answers to that: a physical answer in energy, and an answer that takes the human eye into account. For screens, the second one counts. This article explains the difference, with lumen, candela, lux and nit.
Vision and perception
The human eye: how we see a screen
An LED screen exists only thanks to the eye that looks at it. Anyone who wants to understand screens therefore starts with the eye: a surprisingly camera-like organ with two kinds of light cells for day and night.
The cone of vision: where a screen does and does not stand out
We are far from seeing everything equally sharply. Straight ahead our vision is crystal clear; off to the side it quickly turns vague. That sharp zone, the cone of vision, determines whether a sign along the road is noticed at all.
Perception: how the brain creates images
The eye delivers only a flat, two-dimensional image. Yet we see a rich 3D world. The brain fills in the rest, using clever rules of thumb. That explains why we effortlessly read separate LED dots as letters.
LED displays
Anatomy of an LED screen: from chip to cabinet
An LED screen looks like a single whole, but it is a build-up of layers: from the microscopic chip that makes light to the watertight cabinet that protects everything. Here you see every level.
Pixel pitch and legibility: connecting dots into an image
Pixel pitch is arguably the most important property of an LED screen. It determines how sharp the image is, how close you can view it, and how much it costs. Here you read how that all hangs together.
Calculating viewing distance: character height, speed and time
‘How big must the screen be?’ is the wrong question. The right question is: how far must it be legible? That depends on the character height, the viewer’s speed and the time they need to read.
Viewing angle: how widely a screen spreads its light
An LED shines brightest straight ahead. From the side the screen looks darker. How wide that bright zone is, the viewing angle, you largely determine with the lens and the choice of LED.
The value of LED: reliability and energy
An LED screen looks expensive to buy. But over its lifetime that picture tilts: high reliability and low energy consumption make it more cost-effective in the long run than the alternatives.
AlphaEclipse outdoor signs: anatomy and readability
An AlphaEclipse outdoor sign is built from a grid of LED pixels. Using the original Adaptive diagrams, this article shows how a pixel is made up, which character size you need for a given viewing or driving distance, and why LED signs are more readable both day and night.
Modern LED technology
Discrete (DIP) versus SMD LEDs
The way the LEDs are packaged determines almost everything about a screen: how sharp, how bright, how wide the viewing angle. The major divide is between the older discrete (DIP) LED and the modern SMD LED.
COB, IMD and fine pixel pitch
Screens you can stand right in front of without seeing dots require an extremely fine pixel pitch. Two technologies make that possible: COB, in which bare chips are encapsulated, and IMD, in which several pixels sit in one package.
White versus black LED: contrast and sunlight
The colour of the packages around the LEDs, white or black, seems a detail, but helps determine how deep the black is and how legible the screen stays in bright sunlight. Black almost always wins there.
Grayscale and colour depth (bits)
A screen that shows beautiful, smooth colour gradients without ugly ‘stripes’ has many grayscale levels. We call that wealth of brightness steps per colour the colour depth, expressed in bits.
Refresh rate and image refreshing
An LED screen rebuilds its image many thousands of times per second, far too fast for your eyes. But a camera can catch the screen right in the middle of such a refresh, resulting in flicker stripes on video. A higher refresh solves that.