Modern Displays Up Close
This article has a video version which you can view here.
This is an iPad under a low-power microscope. You’re seeing the pixels of the liquid crystal display (LCD), each composed of red, green, and blue subpixels. There’s a light behind these pixels - the backlight - and by darkening the subpixels in varying amounts, you can create a wide range of colors, which is the principle behind most color displays.
Because of this, we can create some neat moving patterns, visible only this close, by shifting hues.
On this iPad, the LCD subpixels have a chevron shape - the red and blue subpixels together bear a strong resemblance to the Chevron logo, albeit pointed in the wrong direction. Each pixel is absolutely miniscule, yet you can see there’s fine detail in them. LCDs are manufactured using photolithography, a technique also used to make integrated circuits. That’s how each pixel and subpixel can be so sophisticated and precisely manufactured.
You probably also noticed the large amount of seemingly unused black space between the rows of pixels and around the subpixels. This is called the black matrix; it’s needed to separate the subpixels from each other and prevent light leaking between them, and it apparently also increases contrast. As to why it takes up so much space between the rows of pixels here, while taking up little space between subpixels, I’m not sure.
The word “if” displayed on an iPad.
Here you can see how small text is displayed on the iPad. You can see that there are some dimmer pixels at the edges of the characters; this is anti-aliasing, used to make the text look smoother.
Liquid crystal displays have a few issues, the biggest one for me being that they typically aren't great at displaying black - instead it’s visibly gray, at least in a dark room. An alternative display technology is OLED - organic light-emitting diode. They’re just like traditional LEDs - light-emitting diodes - but they come from the organic section of the grocery store (that’s a joke, but actually, OLEDs are fundamentally different from traditional LEDs).
OLED displays are used in a wide variety of devices, including televisions, smart watches, and phones, like mine, which you see here.
The pixels of an iPhone 14 Pro Max.
Clearly the design of the pixels is different. This isn’t strictly because it’s OLED, but this layout is common with them. This is called a PenTile matrix; a Samsung-trademarked term where the PenT- comes from the Greek “penta,” meaning five, because the original design had a repeating layout of five subpixels - two green, two red, one blue - although the design on this phone uses a four-subpixel layout.
There’s a very good reason for this layout… probably. See, I had a nice and neat answer, but after doing more thinking and research, the reasoning became murkier. So here's part of the answer: the human eye generally is more sensitive to and sees more detail in green than in red and blue. So, by using more green subpixels and fewer red and blue subpixels, you can take advantage of human biology to display what is perceived as more detail with fewer subpixels. In fact, a layout similar to this is used on most digital camera sensors for the same reason, where it's called a Bayer filter.
You’ll also notice the subpixels vary in size and shape. Unlike LCDs, which (usually) work by selectively darkening the light behind them, OLED subpixels actually generate the light themselves, which means that to display black, they can simply be turned off. This is what allows OLED displays to have much darker black levels than typical backlit LCDs. But in order to do this, OLED subpixels have to have specific chemical compositions to produce those colors, and it seems that blue OLED subpixels are especially inefficient and prone to degrading, so they're made bigger to compensate.
Are you getting tired of the word “subpixels” yet?
Despite having a decent idea of how they're made, I’m still astonished by the level of precision in these displays. On my phone the subpixels are so small that even looking closely, I can only get the faint impression of a grid layout.
For completeness, here’s what text looks like up close on this phone’s screen.
Just for fun, let’s look at some pictures I took a while back of another LCD - that of my Game Boy Advance SP. This was actually difficult to photograph because the light on the screen is pretty faint - I have a front-lit model, and I’m sure a backlit model would look better. Attempting to light the screen externally could only help so much because the microscope objective blocked most of the light from the section of the screen under it.
The pixels are pretty big compared to the iPad and iPhone, obviously. In fact, we can make a direct comparison, and you can fit about nine iPad pixels in a GBA SP pixel.
A split comparison of the GBA and iPad Air screens. The colors are a little off due to editing.
You can see a kind of grain pattern in each subpixel; they look random, but comparing subpixels shows that the pattern is actually identical between each one. I don’t know what these are.
I like to make my own backgrounds for my devices - I prefer to have as a backdrop something that I’ve had a hand in creating. On my iPad and iPhone, some of my favorite backgrounds are their own displays.
A month on from taking this photo, I still have this set as my phone background. It looks so cool in person.
According to some kind of fixed-point theorem, some part of the display here is displaying itself. It might be a subpixel, or black matrix, but it’s there. On a meta level I just think it’s kinda funny to have a picture of a display on the display as a background. It’s showing you what you’re looking at.
If you liked these images and want some in high quality to use as backgrounds, you can head over to my Patreon and download them by joining with the $2 tier. To be clear, you can sign up for a single month, download the images, and have them forever.
Of course, you could also just save the images in this article - I can’t stop you - but the images on my Patreon are higher-quality, and supporting me helps me to create more content like this.