You’re shopping for electronics online, trying to order some voltage regulators for your next trip overseas, when you get side-tracked looking at TVs. You scroll through the various offerings, trying to ascertain the difference between LED and LCD technology beyond the price tag, and, after a few minutes, you decide to go see for yourself at the local big box electronics store.

Once you’re there, the salesperson gives you a brief rundown, but, ultimately, they’re just reading information off of a product card; you can tell they don’t have a real grasp of the differences. Also, they’re definitely going to try to sell you the most expensive thing—even if you’re just looking for information and planning to buy online later, this person probably isn’t the most reliable source.

So, what’s the difference? Just like with voltage converters and the 110 to 220 transformer you bought for your last trip overseas, it’s important to understand how this technology works before you make a purchase in order to make sure you’re getting the right tool to suit your needs.

Understanding LCD: Polarized Light And Liquid Crystals

LCD stands for “liquid crystal display.” These types of displays are absolutely everywhere in our world, from the cell phones in our pockets, to the monitors on our desks, to the informational screens at the airport. LCD screens work by using liquid crystals to rotate polarized light, either facing it out to help create a picture or keeping dark to create blacks and contrast.

“Liquid crystals” sounds like something that shouldn’t exist; after all, we’re taught in school that matter exists in one of three states at any given time: solid, liquid, or gas. Matter may transition between states when heat, pressure, or another catalyst is applied, but it can only rest in one of the three states—at least, this is what scientists thought up until the end of the nineteenth century.

Liquid crystals were first discovered in 1888 by a botanist named Freidrich Reinitzer. His experiments with a chemical known as cholesteryl benzoate led to the revelation that certain types of matter didn’t always behave exactly as expected, and, when heated specifically to the right temperatures, a liquid crystal state could be induced. It took eighty years, but, in 1968, RCA finally developed the first experimental LCD system, revolutionizing the way we think about displays.

A steady stream of new developments over the course of the following decades led to the ubiquitous LCD screens that we know and love today. While vastly more complex than the initial RCA prototypes, current LCD technology is pretty simple in the grand scheme of things. It’s all about selectively displaying polarized light, which means harnessing light waves and making them behave in an organized manner in order to display the picture that we want.

For example, if you take the lenses out of a pair of polarized sunglasses and stack them on top of each other, you’ll still be able to see through them with clarity since the polarization of the glass in the lenses is parallel, allowing light to pass through.

However, slowly rotate one of the lenses to a ninety-degree angle and look through them both as you do it; you’ll notice that, once a ninety-degree angle is reached, the lenses will completely obscure any incoming sunlight and become totally opaque. This phenomenon is at play in every LCD screen you encounter, with the glass screens at the front and back of the display’s construction defaulting to opaque polarization when powered on.

LCD pictures are created by a rear light source, typically fluorescent lamps. Images on the front screen that we view are created by switching off the electricity flowing through specific liquid crystals sandwiched between the ninety-degree polarized glass planes, causing the individual crystals to twist.

This rotates the individual crystal’s light waves to a ninety-degree angle from their default opaque setting, which aligns that pixel with the front-facing glass and allows light from the fluorescent tubes in the rear to flow through that specific spot. Multiply that by millions, and that’s how you get a picture.

It’s a very specific process, but, ultimately, not a particularly complicated one. The most important factor for your purposes in understanding the difference between LCD and LED is that liquid crystals produce no light of their own; they must be backlit in order to serve any purpose as a viewing medium. The type of light involved makes a big difference, for reasons that will become apparent below.

LED: Reinventing the Color Wheel

Many consumers assume that LCD and LED screens are built from completely different technology, especially given the higher price point of most LED screen products. After all, this has historically been the case with display-based advances; the inner workings of an old-school CRT TV are totally different from those within a plasma screen TV, which are, in turn, totally different from those within an LCD TV.

What most people don’t understand is that LED technology is really an improvement upon LCD, not a replacement. To put it simply: All LED screens are LCD screens, but not all LCD screens are LED screens.

LED stands for “light-emitting diode,” which is a fancy way of saying “itty bitty light bulb.” LED bulbs function similarly to regular light bulbs, in that they harness electricity to create light, but the key difference is efficiency; compared to standard bulbs, LEDs don’t really get very hot, and they last for years without having to be replaced. For this reason, LEDs are gradually replacing old-style light bulbs across nearly every industry, including the manufacture of display screens.

LED displays utilize bright, efficient diodes in place of the traditional fluorescent lamps to push light through the liquid crystals. That’s it—otherwise, the TV or monitor functions basically the same as its standard LCD counterpart. It’s like your electric razor when you plug it into a step down voltage converter; it works the same way—there’s just different technology in play.

So, What’s the Difference?

Broadly speaking, LED screens are almost always going to look better than regular LCD. That doesn’t mean that there’s anything wrong with LCD; after all, they still represent the best current technology for display creation. It simply means that displays which utilize LED lamps instead of fluorescents tend to have better picture quality.

First and foremost, LED screens are able to create more realistic colors and purer, truer contrast due to the placement of the diodes and a technique called “local dimming.” With fluorescent-backlight LCD displays, the backlighting lamps are always blazing away at full power, so, if an area of the screen needs to be a dark color or totally black, the liquid crystals need to be totally activated in order to block the full-power light of the tubes.

The problem is that LCD panels aren’t all that great at blocking their bright backlighting, which can lead to slight issues depicting heavily shadowed scenes or images. The classic example is a shot of outer space, which would involve a largely black screen with tiny bright dots in the form of stars; this is very difficult for a traditional LCD to accomplish.

Locally dimmed LED screens get around this by varying the brightness of the individual LEDs lighting the display from the back or the sides. That same shot of space will have a much deeper and more consistent black background since the lighting behind and around it can be dimmed instantaneously, allowing the liquid crystals to do their job with relative ease.

Another consideration is energy efficiency. LEDs require significantly less power than their fluorescent LCD counterparts, so, if the display in question is something like a monitor for your work computer or waiting room TV, which will be powered on for most of the day, LED lighting will be more cost-effective in the long run, even considering the typically higher up-front price tag that comes along with the technology.

Ultimately, it’s a matter of personal preference and intended use. If you’re building a carefully tuned home theater system that will be used to regularly screen modern films, with ambient light balance and optimum viewing distance taken into consideration, an LED system is probably going to be worth it since they are much easier to adjust to any particular room’s settings.

If you’re buying something small to use with a 110 to 220 converter on your next overseas business trip, an LCD will probably do you just fine.