What are TV Backlights?
Screens are more than just the flat color panel that we see in the end. There are a few different pieces stacked behind that image. Besides OLED panels, LCD and LED panels have backlights, a polarizer, TFT glass, liquid crystal, a color filter, and a polarized layer.
The backlights are meant to provide the brightness that brings the color to the forefront. Here are the five types of backlights:
- LED (light-emitting diodes)
- ELP (electroluminescence panels)
- Hot CFL (cathode fluorescent lamps)
- Cold CFL (cathode fluorescent lamps)
- Incandescent light bulbs
While each type of backlighting uses a different light source, they have to be arranged in a particular way to properly direct the light into the color filter and through the other layers. The main three arrangements are called Edge-Lit, Direct-lit, and Full Array.
Today, backlight panels are made from LED light arrangements. In the case of OLED/QLED TVs, backlight panels are entirely excluded.
What is Direct-Lit?
Direct-lit backlighting is when LED lighting is used across the back panel of the TV. It is placed directly behind the LCD panel and provides a uniform light across the screen. It provides a much brighter picture due to heavy LED use. Unfortunately, all that extra light can make darker shades too bright. In some cases, black sections of the screen can appear to be grey. This is a phenomenon known as “elevated black levels”.
Wide-screen formatted films with letterboxing can make the elevated black levels incredibly apparent. As the entire backlight panel is controlled by a single command, there is no way to eliminate the grey tones created in what’s supposed to be black space. As direct-lit arrangements were created as the first step from CCFL to LED backlights, it was a problem that just came with the territory. Which inspired the creation of full array of LED arrangements.
What is Full Array?
In order to combat the elevated black levels of direct-lit panels, LED backlighting using a full array with local dimming (FALD) was created. It breaks up the LED backlight panel into several zones. Each section or zone is responsible for only a portion of the screen’s backlighting. This allows for areas to have local dimming or brightening.
The idea behind providing local dimming was to further increase the contrast and provide deeper shadows, brighter highlights, and more vivid color. The shadows and dark sections of movies stop being grey blocks and match the rest of the image better. FALD TVs are the best arrangement for LCD/LED TVs compared to edge-lit and direct-lit. It provides the benefits of a full light source and evens out the darker areas of the screen to prevent elevated black levels.
Direct-Lit vs Full Array: Side-by-Side Comparison
|What it is:||Backlight panel arrangement||Backlight panel arrangement|
|Primary use:||Provides light for a television screen||Provides light for a television screen|
|Technical committee:||Samsung||Sony, LG, Samsung|
|Influential developers:||Samsung||Sony, LG, Samsung|
|Technologies influenced:||Televisions, monitors||Televisions, monitors|
The Differences Between Them
Full Array and Direct-Lit backlights are placed behind the LCD panel to provide the television lighting. As Full Array is an improved and refined version of Direct Lit, it provides a better image with more vivid colors and higher contrast.
Direct-Lit panels use a simple array of LED lighting that provides a uniform light across the LCD panel in the television. This is great for color and viewing angles, but it has no ability to increase color contrasts aside from dimming the entire backlight.
Full Array backlights are made with sections of LED lights across the entire panel that is controlled dynamically to provide high brightness contrast and even more vivid colors. It completely removes the elevated black levels that plague direct-lit televisions.
During the switch from CCFL to LED backlighting, direct-lit arrangements were created as the first step. A simple set up of LED lights all controlled as one to provide consistently bright light to the LCD panel. At first, the transition was such an improvement that most were happy with the new backlighting. It didn’t take long for enthusiasts and home theatre hobbyists to spot that black tones were hard to achieve. The elevated black levels were just too grey.
That’s when the idea to section the LEDs into separately controllable sections came into being. It allowed for portions of the screen to be locally dimmed which changed the heavily lit greys back into the darker black shades they were intended to be. The new arrangement was called a full array with local dimming. Today, full arrays are still among the most expensive televisions aside from QLED/OLEDs.
Direct-lit is still used to create a cheaper option, but manufacturers also make use of an arrangement known as edge-lit to achieve the same cost as a direct-lit panel without suffering elevated black levels. Unfortunately, Edge-Lit backlighting suffers from a lack of color vividness compared to full array and direct-lit panels.
|Cheapest television backlight panel||Elevated black levels|
|Wide viewing angle||Less contrast than full array|
|Bright image||Can cause screen burn-in easier than full array|
|Better contrast and image detail than direct-lit||If a single LED zone fails, the entire backlight panel fails.|
|Uses individual LED zones to allow for local dimming and brightening||LED zones can not be individually calibrated or controlled.|
|Improves the quality of HDR content||Expensive compared to direct-lit panel televisions.|
|Wide viewing angle|
Direct-Lit vs Full Array: Six Must-Know Facts
- Direct-lit LED backlighting arrangements were set up as the first to replace cathode fluorescent lamps.
- Full array allows for local dimming.
- Direct-lit backlighting suffers from elevated black levels which render darker spaces on the screen a grey color.
- Full array lighting maintains the vivid colors provided by LED direct-lit backlighting.
- Both Direct-Lit and Full Array arrangements place the backlight panel right behind the LCD Panel.
- Direct-Lit televisions are less expensive than full array televisions.