Edge Lit vs Backlit

The next evolutionary step from the huge CRT displays of yesteryear is the LCD display. As LCDs do not produce their own light, they need to be supported by additional lighting. There are currently two ways of providing this light, and the two are respectively called edge lit and backlit. The main difference between the two is in how the lighting is arranged. With backlit displays, the light sources are placed directly behind the LCD while edge lit displays have the light sources placed on the edges with a thin diffuser behind the LCD to disperse the light.

The main advantage of having an edge lit display is the reduced thickness. The diffuser is extremely thin compared to having the actual light sources behind the display. Most of the very thin displays are edge lit rather than backlit and transfer most of the electronic components to a bigger base or stand.

The downside to an edge lit display is the non-uniform spread of the lighting. Even though the diffuser does a good job of spreading it, the light can sometimes be noticeably stronger on the edges. This can be problematic in some scenes like a strong light source in the middle of a very dark environment. As the backlit displays can achieve a more even spread of light, it suffers less from these problems and can sometimes achieve better contrast in those situations.

Lastly, the introduction of LEDs as a replacement to CCFLs may prove to be the deciding factor in favor of backlit displays. The use of LEDs makes it possible to control the light intensity of different areas, achieving very deep blacks where needed by turning off the LEDs behind that area. Edge lit displays, even when utilizing LEDs, can only take very minimal advantage of such techniques due to the non-even placement of the LEDs. In the scene mentioned above, the sides would still get a very low contrast as the LEDs need to all be lit in order to achieve the brightness at the center.

Summary:

1.Backlit displays have the light sources spread out across the entire display while edge lit displays only have them on the edges.
2.Edge lit displays tend to be thinner than backlit displays.
3.Edge lit displays tend to suffer more from non-uniform contrast than backlit displays.
4.Backlit displays provide better contrast than edge lit displays when using LEDS.

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