The Truth About So-Called LED TVs

Don't get confused when buying your next TV

There has been a lot of hype and confusion surrounding the marketing of "LED" TVs. Even many public relations representatives and sales professionals that should know better are falsely explaining what an LED TV is to their prospective customers.

The following information applies TVs made by a variety of manufacturers including, but not limited to Hisense, LG, Panasonic, Samsung, Sony, TCL, and Vizio.

Vizio Full-Array Active LED Zone Illustration
Image provided by Vizio, Inc.

What an LED TV Really Is

To set the record straight, the LED designation refers to the backlight system used in many LCD TVs, not the chips that produce the image content.

LCD chips and pixels don't produce their own light. In order for an LCD TV to produce a visible image on its screen, the pixels have to be "backlit."

For more specifics on the backlighting process needed for LCD TV, read Demystifying CRT, Plasma, LCD, and DLP Television Technologies.

At their core, LED TVs are still LCD TVs. The difference between the two is the backlight system used. Most LCD TVs employ LED backlights rather than fluorescent-type backlights, thus, the reference to LED in TV advertising hype.

To be technically accurate, LED TVs should be labeled and advertised as LCD/LED or LED/LCD TVs.

There are currently two ways that LED backlighting is applied in LCD TVs, Edge Lighting and Direct Lighting.

LED Edge Lighting

Edge Lighting consists of a series of LEDs are placed along the inside edges of the LCD panel. The light is then dispersed across the screen using "light diffusers" or "light guides."

  • The advantage of this method is that the LED/LCD TV can be made very thin.
  • The disadvantage of Edge lighting is that black levels are not as deep and the edge area of the screen has a tendency to be brighter than the center area of the screen.
  • Sometimes you may see what is referred to as "spotlighting" in the corners of the screen, and/or "white blotches" scattered across the screen. When viewing daylight or lit interior scenes, these effects are not usually noticeable. However, they can be noticeable when night or dark scenes in a TV program or movie are viewed.

LED Direct Lighting

Direct or Full-Array (also referred to as Full LED) consists of several rows of LEDs placed behind the entire surface of the screen.

  • The advantage of the full-array backlight is that it provides a more even, uniform, black level across the entire screen surface without white blotches or corner spotlighting.
  • Another advantage is that these sets may employ "local dimming" (if implemented by the manufacturer). Full-Array Backlighting combined with Local Dimming is also referred to as FALD.

If an LED/LCD TV is labeled as Direct Lit, this means that it doesn't include local dimming, unless there is an additional qualifier. If an LED/LCD TV incorporates local dimming, it's usually referred to as a Full Array Backlit Set or is described as Full Array with Local Dimming.

When local dimming is implemented groups of LEDs can be brightened or dimmed independently within certain areas of the screen (sometimes referred to as zones). This provides more control of the brightness and darkness for each area, depending on the source material being displayed.

Sony's Backlight Master Drive provides dimming of each individual LED.

Another variation on full array backlighting with local dimming is Mini-LED. Mini LEDs work like "standard" LEDs but are much smaller. This means instead of just a dozen or a few hundred LEDs, Mini-LEDs can number in the thousands and can be grouped within hundreds of zones.

This allows even more precise brightness and contrast control for both bright and dark object elements, such as eliminating white bleeding from bright objects on black backgrounds.

TCL's Quantum Contrast labeled TVs are examples that use mini-LED technology.

Local Dimming In LED Edge-Lit LCD TVs

Some edge-lit LED/LCD TVs also claim to feature "local dimming."

  • Samsung uses the term micro-dimming. 
  • Sony uses the term Dynamic LED (on TVs that don't have Blacklight Master Drive).
  • Sharp refers to their version as Aquos Dimming. 

Depending on the manufacturer the terminology used may vary. However, the technology employed consists of varying light output using light diffusers and light guides, instead of large numbers of LEDs directly behind the screen. This method is less precise than FALD.

If you are considering an LED/LCD TV, find out which brands and models use Edge or Full Array backlighting and see which type of LED backlighting looks best to you.

LED/LCD TVs vs Standard LCD TVs

Since LEDs backlights are designed differently than fluorescent backlight systems, this means that LED-backlit LCD sets have the following differences with standard LCD sets:

  • Lower power consumption
  • No mercury used as in some other LCD backlight systems
  • More balanced color saturation
  • In LED/LCD TVs using the Full Array blacklight method, there is little or no light leakage in dark scenes. This contributes to even better black levels than traditional or LED Edge-lit LCD televisions.
  • LCD TVs that employ Full-Array or Direct LED backlighting are thicker than LCD TVs that employ an Edge-lit LED light source.

LEDs and Quantum Dots

Another technology that is being incorporated into a growing number of LED/LCD TVs is Quantum Dots. Samsung refers to its Quantum Dot-equipped LED/LCD TVs as QLED TVs, which many confuse with OLED TVs. However, don't be fooled—the two technologies are different.

In brief, Quantum Dots are man-made nanoparticles that are placed between an Edge-Lit or Direct/Full-Array LED Backlight and the LCD Panel. Quantum Dots are designed to enhance color performance beyond what a LED/LCD TV can produce without them.

Samsung is spearheading a move to develop TVs that combine Quantum Dots with OLED. This is referred to as QD-OLED.

Digital Signage and Micro-LED

The only true LED-only video displays, are the ones you see in stadiums, arenas, other large event venues, "high-res" billboards, a small number of cinema screens, video walls, that employ technologies such as MicroLED in which the "LEDs" display image content directly by generating the light, the color, an image content.

LG MicroLED Video Display Demo
LG

LED Use in DLP Video Projectors

LED lighting is also being used in DLP and to a lesser extent, in LCD video projectors.

An LED light bulb(s) supplies the light source instead of a traditional lamp. In a DLP video projector, the image is produced in a grayscale form on the surface of the DLP chip, in which each pixel is also a mirror. The light source (in this case an LED light source made up of red, green, and blue elements) reflects light off of the DLP chip's micromirrors and is projected onto the screen.

Using an LED light source in DLP video projectors eliminates the use of a color wheel. This eliminates the DLP rainbow effect (small color rainbows that are sometimes visible in a viewers' eyes during head movement).

Since LED light sources for projectors can be made extremely small, a new breed of compact video projectors, referred to as Pico projectors have become popular.

Video Projector LED Light Source Generic Example
NEC

LED Use In TVs, Present and Future

Since the demise of Plasma TVs, LED/LCD TVs are the dominant type of TVs available to consumers. OLED TVs, that use different technology, are also available, but have limited distribution (As of 2019, LG and Sony are the only TV makers marketing OLED TVs in U.S. Market), and are more expensive than their LED/LCD TV counterparts. With the refinement of local dimming and Quantum Dots, the future of LED/LCD TVs is very bright.