LED Backlighting vs. Edgelighting

Okay, I am now in the grip of Scott terror! I have a wonderful opportunity to buy several televisions for my home, and I have listened to your moments with Leo Laporte (which are just the best!) and read what you've written. As I see it, your recommendation is first plasma (if conditions permit) and second LED LCD. But I'm not sure if you prefer LEDs around the edges of the screen or full LED backlighting.

Herman Tarnow

There's no need for terror; I won't bite! And thanks for your kind words! You are correct, I generally prefer plasma if you have some control over the ambient light in the room and don't have a window or lamp directly behind your viewing position. And I do prefer LED-illuminated LCD TVs over CCFL-illuminated models.

As for LED edgelighting versus backlighting, I strongly prefer backlighting, because edgelighting usually results in poor screen uniformity, especially in dark scenes. Such images usually have lighter and darker areas because it's nearly impossible to distribute the light from LEDs at the edges evenly across the entire screen. By contrast, LED backlighting often results in much more uniform illumination in dark scenes.

Also, LED backlighting typically provides a feature called local dimming, in which the LEDs behind dark portions of the image are dimmed to make then darker, which yields much greater contrast and better perceived blacks. However, this is not a panacea—the LEDs are dimmed and brightened in relatively large clusters or zones, so things like stars or white text on a black background can look like they have halos around them. As you can see in the illustration above, the "backlight simulation" shows what the image would look like if you were looking only at the LEDs, which form a black-and-white image with much lower resolution than the final image on the LCD panel itself.

Plasmas don't have any of the problems that LCDs try to overcome with various technologies, and they have no off-axis picture degradation that all LCDs suffer from to one degree or another. This is why I prefer plasma over any type of LCD as long as you can deal with plasma's shiny screen.

If you have an A/V question, please send it to askhometheater@gmail.com.

johnnyd's picture

I prefer a highly detailed TV picture, and hate the screen door effect of plasma (Kuro included)! Maybe others don't notice it, but I do! I seriously doubt plasma can come anywhere near the fine pixel pitch of LCD. 4K sets will be nearly impossible for that tech! With plasma you can make out the pores on peoples faces. With LCD you can take an all day tour inside the pores! Give Me Detail, or Give me Death!!!

SunriseGatefield's picture

Assuming that by "screen door effect" you mean what some others call the "dirty screen effect", while you are correct that some see it on plasmas, it is also an issue with some LCDs, even high-end ones.

johnnyd's picture

Not for me!