LCD TV Series 2

LCD / LED-LCD / OLED TVs..

Last week I wrote about Full HD / HD ready and got lots of response. So thought of writing about LED TVs

Most of you must be aware that the so called LED TVs are really not LED TVs. This is just a marketing gimmick to push their LED backlit LCD TVs. The real LED TVs are yet to come in large screens or at affordable prices and is known as OLED TVs. As of now the max size of commercially affordable OLED TVs is less than 30”.

What is the main difference between these? LCDs will not emit light unlike CRTs and it needs some other light source to illuminate the scene, LCD just act as a filter. The backlight can be CCFL (ex: an array of tube lights behind the screen!) or LED can be used for the same purpose. But LEDs are used as a (back) light source for LCD TVs in different ways which will be explained below. So all LED-LCD TVs are not created equal so there is lot of different in price too. LCD screen is acting as filter for the backlighting cannot filter out completely the light for a dark scene, some light will escape through the LCD filter so the dark will not be completely black so the contrast ratio suffers. This explains why the contrast ratio of a Typical LCD TV is less than a CRT or Plasma TVs. This is one of the reason why Pioneer Kuro Series is the king of TVs.

Normal LCD TV with CCFL Backlighting

CCFL gives the source of light and the diffuser will make it evenly bright. This consumes lot of power, A typical 40” TV will consume around 230W and with its mercury content it perceived not very eco friendly.

LED Backlit TVs

The LED back lit comes in different ways and manufactures use their own jargons to confuse the customer.

1. Edge lit LEDs (White LEDs), most common and cheapest.

2. Dynamic RGB LED Backlit (Sony)

3. Dynamic RGB LED Backlit with dimming (Sony)

4. Full Array LED with local dimming (White LEDs)

5. Edge Lit LEDs with local dimming (This is a new avatar to confuse the consumers more )

6. Precision Dimming by Samsung (It is same as 4)

7. Dolby vision (May the best, Implementation will be very costly)

Edge lit TVs

White LEDs are placed at the edge of the screen and the diffuser will make the screen evenly lit. This has the advantage of 40% reduction in power consumption compared to CCFL lighting. Screen is thinner compared to all other technologies and more eco friendly. It gives better brightness and contrast levels compared to CCFL backlighting. So picture quality is noticeably better for HD video. All LED TVs available in India belong to this category.

Full Array Bcklit

Here there will be an array of LEDs in the back of the LCD screen. This Full Array LEDs acts as the souce of light resulting in even lighting. So this gives a better picture with a thicker TV compared to edge it Nobody wants to offer Full array with out local dimming now.

Backlit LED TVs

Full Array Backlit with Local dimming

With Full Array Backlit we have the advantage of putting LEDs ON and OFF depending on what is happening in the video (the brightness of the scene). . In other words, you can dim certain areas of the screen, while keeping other areas bright. In the simplest form, picture a split screen with black on one side and white on the other. Local dimming would allow the LEDs on the black side to be off and the LEDs on the white side to be lit. This has the advantage of better contrast ratio since LEDs are put off locally (selectively) when the scene is dark. So no amount of light will filter through LCD screen. Now how many LEDs you want to use to cover the backlighting. More and more LEDs used in the Full array results in finer control of the scene as explained in Dolby Vision below. This will reduce the power consumption further.

Backlit Full array LEDs

Dolby Vision (Full Array LED Backlight with local dimming)

Dolby vision is from Dolby Laboratories. After the initial video processing (de-interlacing, interpolation / inserting and dropping frames to fill the gap, scaling) Dolby vision takes over. It apparently analyze each frame and add another 8 bit for luminance (brightness) to the 24bit used for deep color (ex: 8 bit going to LED array and 24 bit to LCD screen) and create an low resolution image in backlit LED array and corresponding high resolution color image in LCD screen thus recreating the scene. Since LCD screen is super imposed on the LED image you get much better contrast ratio to rival Pioneer Kuro Series Plasma TVs.

Figure showing LED image with super imposed LCD image.

The number of bits and LEDs used in LED array varies to give finer control and different pricing. All the TV manufactures offering Local dimming is using this technology using different number of LEDs resulting in variation of finer controls and thus pricing. So customer life is not going to be easy to select a LED TV L

EDGE LED with local dimming

Apparently Full Array LED with local dimming is a costly affair as seen in Samsung 8500 series and yet to release Sonly HX900 series. So they have come up with another version of local dimming by putting ON and OFF the EDGE LED depending on the Video. There is no fine control here and the effect is almost column wise and the application is for very limited scenes. This is another marketing gimmick to use the term “Local Dimming” and charge more from the customer. LG 9000 series and Sony LX series tend to go this way……

Hope this clarifies the myth of LED TV. Read more in http://blogs.ad.infosys.com/users/tomy_thomas/

Subject: Full HD or HD Ready or HD Ready 1080P

I could see lot of debate on LCD TVs and its resolution recently. So I thought of sharing my firsthand experience.

You may think Full HD is (1080P) 1920X 1080 pixels resolution and the so called HD ready TV can show 720P and 1080i. But it is a loosely defined and one of the most abused term. The definition is not same in US and Europe. So look at the specification which will reveal more. For ex: Sony markets their HD camcorders as Full HD but it can shoot video at 1080i only not 1080P. In some parts of the World HD ready means it is capable of accepting HD material but no built in HD tuner.

But for discussion we will stick to these definition ( Resolution of HD Ready TVs is 1366 H x 768 V = 1 million pixels= 720P, Resolution of Full HD TVs is 1920 H x 1080 V = 2 million pixel= 1080P.)

Do you need a full HD TV?

Short answer: NO. You need a Full HD TV if you satisfy one of the following conditions.

1. You use your TV as a computer monitor and the graphics card supports 1080P or more.

2. You are ready to spend plenty of money (more than the cost of your TV) on source material. Bluray movies (nothing else, comes in 1080P as of now). All the so called HD DTH gives only 1080i not 1080P ex: Sun HD or any other DTH provider who are planning to give HD in future. I need to add SUN HD gives 7 channels in HD out of which 5 are true HD and two are upscaled mostly nwith 4:3 aspect ratio.

3. You are investing on a TV for next 5+ years or more

80% (90%?) of the PS3 games comes in 720P not 1080P. Normal human eye cannot distinguish between 720P or 1080P at a distance of 12’ for a 40inches TV. You need to sit closer 6’ to really appreciate the difference. The distance calculation is totally different for SD and HD TVs. You need to sit much more closer to HD TV showing HD material to appreciate the difference.

Do not get fooled by the clarity of demo videos showed in the shop. It is shot with much higher resolution digital movie cameras (ex: RED, 4K resolution) and converted to 1080P, so you will never see such clarity even in Bluray movies. You can download these demo videos of any manufacturers at home from the site http://www.demo-world.eu under trailers Full 1080P section. If you need I have plenty of them with me, at least 5GB.

Resolution for the commonly used video material.

DVD: 576P

DTH SD: 576i most cases Sun gives 576P but it is not better than Tata Sky+

SUN HD: 1080i

Digital 8 / Mini SD Camcorder : < 330 lines

HD Camcorder: 1080i

Most downloaded stuff (read torrent) can be 720P or 1080P but during due to poor conversion it loses most of its clarity and a good DVD picture is better an 720P downloaded .MKV movies.. You may tend to argue with me if you use a smaller 32 /40” TV, but nobody can miss the difference in my 52” TV, Sony KDL-52NX800.

But now most of the TV manufactures are offering 1080P at very low prices. So please go ahead and buy it but do not expect any great video unless you start investing on HD videos (Blurays). DTH video is pathetic in many of these TVs (directly proportionate to the size of your TV) even if you do upscale this to HD. Infact most of the systems upscaled DTH video is worse than the original. Again you need to live with the aspect ratio issue. Most of the current DTH material is in 4:3 so you need to stretch the video to fill your 16:9 LCD TV. After some time you may get used to it J

There is a myth that Sony TVs are the best. It is not at all true. All AV gurus / gadget freaks knows that Pioneer Kuro Series Plasma TVs are widely considered as the benchmark / reference TV. Every other TV out there is aspiring to become a Kuro. I am not denying the fact that there are challengers like Mitsubhishi Laser TV, but not yet got wide acceptance…

Even Samsung is ahead of Sony in LCD TV technology as on today. Latest hot TV technology is LCD TV using Scattered LED with local dimming (not edgelit LED or CCFL) as backlight and 3D. Philips, Samsung and LG have TVs using LED with local dimming. Samsung 8500 series is supposed to be next to Kuro for clarity in video. Unfortunately it is not marketed in India. Samsung wants to be low cost player here. Philips 3D TV does not need glasses but the drawback of narrow viewing angle. Sony has an answer with their latest Signature series HX900 (not LX900) which is planned to be launched in US in this June ’10.

I have invested a lot in Sony, Apple and Philips gadgets thinking that they are very reliable products. Sony is anyway not known for features. I still have very high opinion about Apple and relatively good experience with Apple. But I had issues with these too, One 29CRT Philips TV model had a design defect which they refused to acknowledge. Sony’s latest product 52” TV KDL-52NX800 TV had showed a panel defect within two days of delivery. They are kind enough to replace it within one week. But I have very good experience (read reliability, not features) with most of their other products including their signature series (X) 40”TV ..

Last week Sony surprised me with a killer product at a killer price. Sony BDP-S370 an excellent Bluray player for Rs 9900/- So many things good about it ……..

Regards,

Tomy