Friday
Jan222010
Jan 22 Podcast #409: LED TV Technology
When we first started our podcast there were five competing technologies vying for your living room. Today its pretty much down to LCD and Plasma. Most would say LCD is running away with the market but Plasma is hanging in there. So what about LED? LED is not a new TV technology but rather a different way to light the LCD. A Liquid Crystal Display is a glass panel that works by controlling the opacity of segments of itself by varying the electrical signal. Each individual segment, called a pixel, acts as a shutter to control the amount of light being passed through. The light source is what we will be focusing on today.
Listen to the show
Today's Show:
News:
- DVRs In 44% By 2015
- Target Offers $99 HDTV Installations
- 3D-Capable TVs to Achieve 1.2M+ Shipments in 2010, 15.6M in 2013
Other:
- Top Netflix rentals in 2009 for certain metro areas by zip code
- Sony Japan intros PS3 DVR, digital tuner
LED TV Technology
When we first started our podcast there were five competing technologies vying for your living room. Today its pretty much down to LCD and Plasma. Most would say LCD is running away with the market but Plasma is hanging in there. So what about LED? LED is not a new TV technology but rather a different way to light the LCD. A Liquid Crystal Display is a glass panel that works by controlling the opacity of segments of itself by varying the electrical signal. Each individual segment, called a pixel, acts as a shutter to control the amount of light being passed through. The light source is what we will be focusing on today.
Background
On current LCD TVs, fluorescent lights are used to back-light screens. You may have seen the acronym CCFL, it stands for Cold-Cathode Fluorescent Lamp and these types of lamps can even be used to light your home. To back-light TVs, a series of these lights are laid horizontally across the back to the TV.
There is typically a plastic sheet in front of the light which will distribute the light evenly onto the glass panel. One of the difficulties in LCD TVs is creating true black. The reason for this is that the light is always on. To darken a screen the light must be blocked and as hard as manufacturers try some light bleeds through.
LED
LEDs have recently become a popular means for lighting LCD screens. Some of the advantages for moving to LED are size, power, and image quality. LEDs are smaller than the CCFL tubes and they use less energy. A side benefit of using less energy is that the TV produces less heat which can extend its life. Better picture quality depends on what style of LED lighting is used.
There are two styles of LED lighting, edge or direct mount. Edge lighting, as the name implies, arranges the LEDs along the edge of the panel. Because the LEDs are mounted on the edge the TVs are much thinner. The light is channeled behind the glass using guides to provide even lighting. The disadvantage of edge lighting is that you can not use local dimming to increase the TV's contrast. You still get the energy and size benefits however.
Direct lit LEDs place the LED behind the glass. 
There can be as many as 1500 LEDs (depending on the size of the TV) placed in an array to light up the slightly more than two million pixels of your 1080p TV. Each LED can be responsible for almost 1400 pixels (or more on smaller sized TVs). The main advantage of the direct lit LEDs is that the TV can use local dimming. That means if an area of the screen is dark the LEDs can be turned off thereby increasing the contrast.
Because the LEDs are behind the glass they are not as thin as edge mount LEDs. There are two types of direct lit LEDs, White and RGB. White LEDs are simlar to their CCFL cousins in that they produce white light. The Samsung UA40B710 is a TV that uses white LEDs. RGB LEDs use three colors (red, green, and blue) which make TVs with this kind of light capable of a broader color range. Those who favor this type of LED say that there is less green push. Sony uses RGB lights in their BRAVIA LED TVs.
Some things to consider
- LED color consistency - It is difficult to make LEDs in consistent white color and this may affect your picture. Manufacturers will not take back a TV because the color is slightly off. You could try to return it to BestBuy until you get one that is perfect.
- Some Edge Lit TVs have uneven lighting. Again try explaining to the manufacturer that the TV lighting seems uneven. You can also do the Best Buy thing with this one too.
- Reliability? We've all seen the LED traffic lights that were supposed to last for 20 years without needing replacement. I stopped counting how many signals have multiple failed LEDs. Will our TVs suffer the same fate?
- Price - Right now you are paying a premium for buying a TV that has a picture that is close to what plasma has always had.
Reader Comments (12)
My fear as an owner of a Pioneer plasma from 2006 is that of burn in. I worry about this if the tv show is broadcasted at 4:3, its against the house rules to watch it or playing videogames for any more then 1 hour, also against the house rules. Do I have to be so ocd with a modern plasma, as I would really like to upgrade and am on the fence between led lcd and just another plasma. Any thoughts suggestions, thanks all.
James:
I've had a Panasonic plasma for a while now (gen 9, the current gen is 12). I have never bothered about what was watched after the first 100 hours. Black bars on top or sides have made no difference. The kids playing video games have made no difference. We have never experienced any burn in or even image retention. At least with a Panasonic, this is not a problem.
Sony's release strategy for their PS3 digital tuner add-ons is really a bit odd.
I would have expected the U.S. or Japan to get this thing first, but instead, they first released one in Europe, followed by Australia and now Japan, but there's still nothing on the horizon for the U.S. market.
Concerning 3D upgrades for regular TVs: I think it is highly unlikely we will ever see such a thing.
In addition to an external box connected with shutter glasses you would definitely need a firmware upgrade to make the TV take a 1080p signal containing 1080i for each eye and displaying this to match the shutter glasses sync.
I don't think TV manufacturers would want to spend their resources developing firmware upgrades for tons of existing TV models just so an hypothetical 3D box could work with them.
Reference your opening comments, I thought you should see this site:
www.twentynot2000.com
For what its worth, II think we should stick with "Twenty Ten", etc.
Also, you may wish to use the target="_blank" tag so that when users click on a link from your site they don't leave your site, but a new browser window opens.
Thanks Guys.
I'm not really seeing an issue with retrofitting 3D on old TVs. The source blue ray or whatever just alternates left and right views while transmitting an IR/rf signal to sync some shutter glasses. The refresh rate is effectively reduced to 30hz. Movies are only 24hz anyway. I really see 3D as another high end feature that anyone who cares about quality will turn off, like interpolation.
Steve in Fort Lauderdale.
Right on guys, there is no great reason to purchase an LED LCD TV when plasma technology is cheaper and often superior to all other television technologies. They do, however, need to start making more < 42" size plasmas or more affordable LED LCDs <42".
I can also vouch for plasma burn-in being a non-issue for all but the most extreme situations. We bought our Panasonic 50" plasma in 2005 (for an exorbitant price compared to today: $3200 vs. a current Sears sale price of $712). When it was new, we did what the owner's manual suggested, and were careful about static images just sitting there, as well as letter & pillar boxing, for about two months. Since then we've barely thought about it, except for the PC I hooked up, which I set to a 3 minute activated blank screen saver. We also took it off factory "torch mode" for optimum picture quality, and that also helps avoid burn-in. We've never had a single issue. Still a FANTASTIC television. It's only with blu-ray where I kinda-sorta get the itch for a 1080p TV to replace it. I'll replace it with a plasma, probably a Panasonic 58".
On my Dad's 2007 version of the same plasma, I did once see some image retention that eventually went away. He and my step-mom often leave it on a weather radar channel. I laughed and told him being a stereotypical old guy was gonna ruin his TV. But it's perfectly fine.
In my office, where I needed a TV to act as basically a second monitor for video editing, etc., I got an LCD just to be sure regarding burn-in, since very sharp menus and windows will stay on the screen for long periods at a time. Plus I happened to find a VERY good deal on a Sony 46" 1080p 120Hz TV. Couldn't resist.
On episode 409 one of you mentioned having limited PVR recording capability.
I have added a 1TB e-sata drive to my Comcast HD-PVR, which adds capacity to the internal 160gb drive.
The drive(s) currently are storing about 200 hours of HD programs, using about 40% of the available storage.
AVSFORUM is the resource for hooking this up.
Not sure if this will work with satellite boxes.
@Steve Hoggarth:
Cutting the framerate in half may seem a solution at first, but the problem is that each eye should be seeing something around 60 Hz.
Shutter glasses at 30 Hz flicker way too much.
Richard,
Could you link to any further info about how to add an additional external hard drive to the Comcast Motorola DVR? Us usual, a search on AVS forum just gives pages upon pages of other people asking the same thing, and no on figuring it out!
I would LOVE to add a hard drive to that thing!
Lee
I've never had a problem with my LG 42" plasma regarding burn-in. I watch alot of SD TV with the annoying black bars on the sides and play video games. If you are that worried just set the TV's zoom / aspect ratio to stretch or something.
I really appreciated the LED segment. I'm a regular listener, but I haven't paid terribly close attention to the latest LCD technologies because I wasn't in the market. But my dad's 35" tube just passed on, and I've suddenly found myself gathering info to help him make an informed decision. I already knew that the sweet spot was in plasma and the better CCFL models, but your synopsis gave me a much better understanding of the LED technologies and has confirmed some of my conclusions.