TV Terms Explained

allajunaki

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So, buying a new TV. Subject to mind boggling amount of information? Let me try and alleviate you frustration let me explain some of these terms for you.

Question 1: LCD , LED , Plasma
First thing first, there are no LED TV's (yet). LED and LCD are both LCD TV's.

So, in LCD TV's we need light (White light, no less) from behind the panel. This light is then gated with help of shutters that control the amount of light passing through them. Color is achieved by puttting color filters on top of this. This is the basic explanation, ofcourse its a bit more complex (OK, A lot more) than that.
But we will go with this simplified explanation.
So remember that we need white light? We call this as backlight. So for the ones advertised as LCD Tv's have a CCFL backlight (Think of it as tubelight in your TV).
LED TV : Replace CCFL with LED lights. Now you have LED TV. Simple!

What are the advantages ?
LED TVs have tons of LED's all over the edge of the panel, compared to 2 (or maybe 4) CCFL lamps need to light up LCD's. This gives manufacturers ability to control lighting on the panel better, because they can turn on/off individual LEDs, also control brightness (Tech is called "Local Dimming"). This improves the black levels of LED Tvs. More on Black levels later.
Another advantage of LED Tv's Cost saving. LED's consume lot less power than CCFL.

Disadvantages of LED TVs:
Generally, viewing angles are lower than LCD TV ( Sorry I do not know the reason why).
Another disadvantage, thanks to trying to make the tv slimmer and slimmer, is uneven brightness on the panel. This is because LED's are all on the edge, and as on 2011, even the best panels have some trouble bringing light all the way to the middle of the panel. So panel will be brighter on the edges compared to the center of the panel. Its not very jarring, but it can be noticed. You will not notice this in showroom because of generally poor viewing conditions. But LED Backlight panels can have better contrast, due to improved black levels.


So What are Plasma? Are they really obsolete?
Let me get this straight.
Are they outdated? NO. A lot of companies are pumping a lot of money into plasma research, for a good reason. Read on to find out.
So what are plasma? In a nutshell, plasma panels create gas plasma to excite phosphors to emit light.
In a nutshell, its an improvised CRT.
The big difference here is, unlike LCDs, plasma do not need a source of light. Phosphors generate light and color. Intensity of phosphor is controlled by intensity of plasma generated behind the phosphor.

Ok, So what are the benefits of Plasma?

Phosphor are much faster to react than LCD's. That means phosphors turn on and turn off really fast (TV manufacturers claim a response time of 0.001ms).

Since Phosphor react faster, its easier to control colors. So its easier for plasma to produce a lot more subtle variation of colors. But some of the high end LCD's will match up with plasma's color fidelity, thanks to some amazing levels to electronic wizardry present in LCD panels.

Better black levels. Remember plasma tv's are self illuminated, this means that panel can switch off the pixels that are not needed. Hence they can produce better black levels (More on this when we talk about black levels).


Disadvantages of Plasma :
Lower end plasmas tend to produce ghosting. That is, phosphors take some time to completely power down, so if there is a white object moving in black background it may leave a small trial behind. This is not very noticeable on any of the 2010 or 2011 panels.

Image retention : If a bright object is static on the screen for some time, it may level a "ghost" of that bright object for couple of seconds after the object disappears. 2010 and 2011 panels have done some magic, that pretty much get rid of this artefact.

Burn In: Will not happen, unless you are planning to use it for showing some timetable or plan to use regular desktop. HTpC's will not cause burn in (Verified by me).


Weak Whites : Plasma TV's have a hard time maintaining peak whites. That is, if a screen has lots of whites, the panel electronics will "tone" down the whites to protect the panel. This is because, if it doesn't the panel will draw too much of power and the panel will literally melt (Remember plasma? Plasma (physics) - Wikipedia, the free encyclopedia ).

Plasmas consume a bit more than LCDs (and a lot more then LED's). But it will be a minor impact on electricity bill. (Say 50 bucks more?) I have 2 plasmas at home :) . This should never be a concern to anyone while picking up tv.

So in essence plasmas cannot get very bright , and LCD's cant go very dark. But if you see, getting dark is more important than getting bright. I will tell you why in a little while.
Also, plasmas are reflective. Bright lights can washout a plasma. Thats why they appear dull in showroom. Some panels do come with anti-glare and anti-reflective coating. They mitigate these issues to a great extend, but glass being glass will still reflect to some extend.

What is Black Level?
Black Level is the darkest the panel can get when showing absolute black on the screen.
LCD's find it hard to hit lower black levels. This is because LCD start with a light, then work on the light to produce all colors. And to show black, they shut out all the shutters. But the shutters are still a bit leaky.
Some of the best LCD panels can go as low as 0.06 cd/m^2 (Most of the LCD's are well above this value, means worse off) . 2011 panasonic plasmas go down to 0.02 cd/m^2. 2011 Samsung Plasma goes down to 0.08 cd/m^2.

At this point, some of you are wondering, if the plasma panel is switching off the pixels, why would it have any light at all. The answer lies in something known as "Cell Initialization". In a nutshell, its like keeping the the pixel in "standby" to wake it up quickly.

Pioneer has cracked plasma equation with a TV they called "Kuro" ( All the videophiles out there have already started jumping up and down, Im sure). Kuro can do a black level of 0.0013 cd/m^2. Reviewer said that the letterbox bars in some of the movies disappear into the dark, while watching movies in dark room. Unfortunately, pioneer exited the TV business. But they did this back in 2008, and we still dont have anything close to it.

White level?
Straight opposite of the blacks, Full white screen.
plasmas, in the interest of not becoming glass art decor in your house, do not do very well here.
LCD's, Its the easy for them, they let let all the light through.
Some of the LCD panels can do peak whites in excess of 250 cd/m^2. you dont have to bother much here, coz anything above will melt your eyes anyway.
Samsung panels for 2011 can do 130cd/m^2. Panasonics do 101 cd/m^2.

So why do I think black levels are more important than whites?
Because most of the homes cannot handle anything above 80 - 90 cd/m^2. If your room is particularly bright, then you may need upto 150 cd/m^2.
BUT, for movie watching (if that is your priority), you will keep your room dark. You will not hit the peak brightness of the panel. But you will need the TV to hit as dark as it can. Black levels also affect all the colors shown by TV.
But of course we need brightness when we are dealing with day time.

In essence, question is when do you watch tv: For evening times Plasmas are fantastic. They do a good job in day time.
In day time : LCD really shine. The good panels do a decent job in the night too.


Plasmas are a bit cheap compared to LCD. However plasmas start at 42", and at that size most of the plasmas are HD Ready panel, not full HD. Im not getting into a debate on Full HD is needed or not :rolleyes:

Guys, I have given explanations as objectively as possible. Please keep this thread civil.

Finally See this :
I thought this article would help someone who has just wet his feat in the world of HDTVs.

The Biggest Mistakes People Make When Buying An HDTV | HD Guru

Thanks dotMac for this post :)

Next edition :
Attempt to explain 120hz 200hz and 600hz (plasmas), and how these numbers dont really mean much.
Contrast ratio advertised is bunch of crap.
3D what right and whats wrong.
 
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