The alphabet soup of TV terminology is overwhelming enough, but you might have seen a particularly confusing term pop up lately: mini-LED. LEDs are already tiny, so what exactly could the "mini" here even mean? It turns out, quite a lot, and that distinction can mean the difference between washed out colors and a more vivid display.
The thing is, almost every TV you see is technically some kind of LED display. Most use bright white LEDs as a backlight, which shines through an LCD matrix and color filter to produce a coherent image. (The exception is OLED, which lights up each pixel individually and thus doesn't require a backlight.)
Mini-LEDs are an improvement over the backlight part of that process. Traditionally, the backlight on most LCD TVs have been either uniform or only divided into a few sub-zones. Mini-LEDs are much smaller back lights that can be individually controlled, allowing your TV to be bright in spots where it needs to be bright, and dark where it needs to be dark.
How do LED displays work?
Before we get to mini-LEDs, let's break down how most LCD displays work a little further. When manufacturers advertise a display as an "LED TV," this is usually referring to the backlight and, well, LED is kind of a given there. However, there are a couple different types of backlights:
Edge-lit backlighting: In this arrangement, LEDs are placed in an array along the outside edge of the screen, which then shine through light guides that more evenly distribute the light across the display. This can be more cost-effective, but it can sometimes lead to light bleed around the edges, or duller areas in the middle of the screen.
Full array backlighting: Alternatively, some manufacturers will create a grid of LEDs that fill the area of the display. This leads to more even lighting across the picture. More importantly, those LEDs can usually be controlled individually, allowing for local dimming (more on that below).
These backlights shine white light (or blue, in the case of quantum dot displays) that is then dimmed or blocked by an LCD matrix. This layer uses tiny liquid crystals to block or allow light to pass through, which then passes through either a red, green, or blue filter. By controlling how much light goes through each of these filters (or "subpixels"), the TV can control what color each pixel will be.
There's just one tiny problem with this: LCDs can't perfectly block all of the light that the backlight emits. This is why, even when your LCD screen is displaying all black, it still looks "on." Some light is always making its way through. In order to achieve darker blacks, you need another technique.
How does local dimming work?
"Local dimming" refers to a range of techniques for LED-backed displays that essentially boils down to the same thing: dimming or disabling backlights where you don't need them. This means less light bleeding through, resulting in darker black levels, and more contrast with the brighter parts of the screen.
The only hitch is, there are quite literally millions more pixels in an LCD display than there are individual backlights. Fewer backlights means less resolution to distinguish between bright and dark zones. It also means you can get what's called a "bloom effect" when a bright object seems to glow more than it should. This is caused when the backlight bleeds through in the dark pixels around a bright object.
Every backlight creates a dimming "zone" and the more zones you have the better. For most LED-lit TVs, this can range from a couple dozen to a few hundred. However, mini-LED tech allows TVs to crank that number up to the thousands.
What makes mini-LED displays different?
Put simply, in a mini-LED display, the LEDs are, well, mini. That's it. To be more specific, the term is defined as any display where the backlight LED diodes are no larger than 0.2 mm. They can be smaller than that, but any larger and they can't (or at least shouldn't) be called "mini-LED" anymore.
When they're packed that small, you can fit a lot more LEDs into the same space. This Sony 65-inch Bravia Mini-LED TV, for example, has over 1,500 local dimming zones. That means that each LED backlight only has to light up a little over one square inch. This provides a lot more flexibility to create contrast between the light and dark parts of the image.
Why would you want mini-LED over OLED?
It does seem a little weird, right? OLED displays light up every single pixel individually, so you're only using the pixels you need. Why this rigmarole with a local dimming array? In part, it's because OLED displays have a higher susceptibility to burn in.
The organic LED elements can degrade in ways that leave ghosting of images that are frequently on screen, such as menus, taskbars, or lower-thirds. This isn't an issue for typical LED-lit displays, where the LCD layer is made of sturdier, inorganic materials.
LED and mini-LED panels can also get a lot brighter than OLED displays. This makes them better suited for TVs that might sit in your living room, near a lot of sunny windows. While OLED TVs exist and they're great, they can struggle to compete with the light in bright rooms, making them better suited to night-time viewing or dimly lit rooms.
