Building Our Digital World, One Pixel at a Time

Nov 17, 2021
8 min read

How do our digital displays even work? Peek into the scientific workings of a tiny pixel.

Written by Tara Yarlagadda
Illustration by Jorge Peña

We are in the midst of a digital revolution that informs every aspect of our lives, but so few consumers actually understand the technology driving this new era of information.

Digital displays make up nearly every facet of modern life, from the droning commercials on TVs to glowing computer screens. Even relatively recent tech, such as smartphones or tablets, rely on digital displays to enable our access to the Internet and connect us to the rest of the world.

But without one incredible microscopic feat, none of this remarkable technology would have been possible.

What is a pixel?

In short: every single image you see while browsing on your computer, smartphone, or any other digital display can be explained by a tiny speck known as a pixel. If you enlarge any digital image, you’ll see tiny tiles—pixels—that make up the image.

Most standard pixels are a fraction of an inch—not even a millimeter in width. It takes many thousands or even millions of pixels to comprise a single image. Pixels serve as the literal building block of all digital displays, ranging from our smartphones to our tablets.

The history of the pixel

“Pixel” is a relatively new term in the English language. The word appeared for the first time in a 1965 article written by American engineer Frederic Crockett Billingsley.

Known as the “father of the pixel,” Billingsley studied and developed image processing for the emerging US space exploration program while working at Caltech’s Jet Propulsion Laboratory. Billingsley coined the term a combination of Pix (Picture) and element (el) in a 1965 paper. From that paper, the modern-day usage of pixels—short for “picture element”—was born.

We’ve come a long way since Billingsley’s research—and it’s not just computer scientists and engineers that rely on pixels for their work. Behind every advertisement you scroll past on social media and every item in your online holiday shopping cart, there are countless pixels, creating our digital world with every click of your mouse or swipe of your finger.

“Pixels serve as the literal building block of all digital displays…”

Researcher Richard Lyon, who reported on Billingsley’s works, summarized the breathtaking impact of this small pixel on humanity:

“Subsequently, pixel has become ubiquitous in the fields of computer graphics, displays, printers, scanners, cameras, and related technologies, with a variety of sometimes conflicting meanings.”

How do pixels work?

But the concept of the pixel goes back even further than Billingsley’s twentieth century research. In fact, the pixel has its roots in the interaction between light waves and the color spectrum, which German photochemist Hermann Vogel explored back in the late 1800s.

Vogel’s research into the sensitivity of colors like green and red paved the way for color photography. We bring up Vogel for an important reason: comprehending how colors interact is essential to understanding how pixels work in real life.

Zoom in close enough on a pixel, and you’ll see that it contains a mixture of RGB, which is short for “red green and blue.” Each pixel contains three alternating stripes of red, green and blue colors. All of these colors will appear under a magnifying glass, but the human eye has far more limitations, so we perceive the light levels of each R, G and B subpixel as a single, merged color.

By changing the luminance—light intensity levels—of these three basic colors and combining them together, we can create an individual pixel with potentially billions of shades. You might be wondering why a pixel contains these three colors—red, green and blue—as opposed to any other set of colors.

“Subsequently, pixel has become ubiquitous in the fields of computer graphics, displays, printers, scanners, cameras, and related technologies…”

For example, most printers for newspapers and magazines rely on cyan, magenta, yellow, and black—colors you’ll recognize if you’ve ever purchased an ink cartridge for your printer. But there are two specific reasons why pixels depend on RGB, and it’s essential to unpack these reasons so you can grasp how pixels work.

First: Color-sensitive cones on our eyes have evolved to pick up wavelengths that correspond to the colors red, green and blue better than any other.

Second: when you mix certain shades of red, green and blue together, you wind up with white light. Mixing these three colors is the most efficient way to make white light—and all the other colors in the natural world.

Every single thing you see onscreen boils down to some combination of these three colors. Whether you’re playing a video game or editing a work project in a spreadsheet, you’re relying on a set of colors that has been broken down from RGB and recreated to appear on your screen.

So, RGB is a natural setting for pixels—the blueprint of our visual displays.

Pixels make up display resolutions

But why do you need to know all this information about pixels? It’s because the pixel can explain the resolution of all modern digital displays.

Resolution can be expressed in pixels per inch—also known as ppi or dpi. For example, 500 ppi translates to 500 pixels per inch.

Photographers and designers resize images to fit the specific display, whether it’s a computer screen or an iPhone. Effectively, the more pixels that a display contains, the sharper an image can appear.

Logically, we can understand this concept. An image of a cat containing one thousand pixels won’t be as sharp as one with five thousand, which provides greater details. Put another way: The greater the number of pixels for a specific display size, the higher its pixel density or resolution.

“…the pixel can explain the resolution of all modern digital displays.”

For example, a cheap 13-inch Windows laptop might contain a resolution of 1366 x 768 pixels, compared to a better laptop with a resolution of 1920 x 1080 pixels. Taking it up a notch, if you mix 25 million red, green and blue subpixels, you’ll end up with 8.3 million RGB pixels total—enough for a modern UltraHD TV.

If you’re still confused, researcher Richard Lyon effectively summarized the difference between resolution and pixels in this simple quote: “Resolution is something you should measure, pixels are something you count.”

What are the different types of displays?

All digital displays rely on the RGB framework of pixels to work, but not all displays work in the same way. There are dozens of confusing shorthand names for the technology within these displays including LEDs, OLEDs, QLEDs, CRTs and LCDs.

You don’t need to know the specifics behind all of these technologies, but it’s helpful to understand the two kinds of basic displays in most consumer products: transmissive displays (LCD, LED, QLED) and emissive displays (plasma, OLED, microLED).

Different technologies make up the displays, but both types of displays rely on pixels to get the job done and allow us to see images on screen.

In transmissive displays, pixels modulate a backlight—the light source behind a pixel—which allows them to block and allow light through. Pixels in transmissive displays function like the shutters of a house, which open and close, blocking and allowing light through to create an image.

“Resolution is something you should measure, pixels are something you count.”

On the other hand, emissive displays generate their own light with no need for a backlight.

Picture turning a light switch on and off, and that’s pretty similar to how pixels function in an emissive display.

How are digital displays changing?

Transmissive displays aren’t 100 percent effective at blocking out light, letting some light leak through. But emissive displays turn completely black when the pixel turns off, resulting in a better contrast—a sharper visual display—on your screen.

But modern transmissive displays, like MiniLEDs, have the added advantage of being able to turn on and off backlights as needed. Through this selected dimming of the backlights, transmissive displays can generate similar dark contrasting visuals as you would find on an emissive display.

Regardless of the type of display, the single most important factor is the quality of light. Poor-quality light results in unclear images. If you’ve ever sat down to a fuzzy image on your TV screen, you know what this feels like. Based on RGB, a display would ideally produce just three colors of light: red, green, and blue.

That’s why blue-emitting LEDs aren’t great for an ideal TV viewing experience. The blue light in the LED mixes with a material to make the light appear white to human eyes. As a result, the white light has to pass through filters to create separate red, green, and blue colors. The end effect: less precise colors such as orange-red or yellow-green.

“Pixels in transmissive displays function like the shutters of a house…”

If you’re looking for a better viewing experience with pristine RGB colors, you’re better off with a transmissive LCD display. Instead of passing through a filter, light from the all-blue LEDs of this display’s backlight mixes with features known as quantum dots to create truly pure RGB white light. Liquid crystals in the LCD pixels further enhance the ability of the pixel’s to accurately control light.

Some emissive displays can also provide a relatively good viewing experience for the modern consumer. A 2021 emissive OLED TV uses blue and yellow light initially before passing those lights through a filter, generating RGB much like the LED LCD.

But unlike the LED TV, the OLED TV adds a white subpixel, leading to brighter light and greater efficiency, though it sometimes sacrifices precise colors in the process. Although emissive displays are more efficient and display better visual contrast in theory, in the real world, both transmissive and emissive displays have advantages and weaknesses to consider.

As quantum dot technology improves, our digital displays will inevitably change as well. But so long as you understand the pixels at work behind the image, you’ll be able to keep up with the changing technology.