Is 240Hz worth waiting for?
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LG's first 240Hz displays with scanning backlight technology will ship in March, and like other 240Hz LCDs they'll confuse unwitting shoppers.
(Credit: LG)Two of the most confusing letters thrown around in reference to LCD and TVs these days are "H" and "z." The confusion will just continue to mount this year, as numerous manufacturers announced 240Hz displays at CES, doubling the 120Hz spec in an attempt to lure buyers. But is it twice as nice?
Until proven otherwise, I'm saying no, 240Hz is not worth waiting for.
Before I get into why, it's probably worth writing a few sentences to sketch out what all these numbers mean. Standard LCD and plasma TVs refresh the screen 60 times per second, or 60Hz, which is plenty fast enough to eliminate flicker and create the illusion of motion from a series of still images. In fact, most sources sent to your display arrive at the nominal rate of 30 frames per second, and each frame is repeated once by the television to achieve 60 total fps.
The problem is that with LCD, some viewers can perceive motion blur in fast-moving objects on standard 60Hz models (motion blur like this isn't an issue with plasma or other display types, whether 60Hz or otherwise, because they use different methods to create the illusion of motion). To reduce blurring, most 120Hz LCD displays use interpolation--called MEMC for "motion estimation-motion compensation"--to create a new frame between each of the original frames, so there's one interpolated frame for every true frame. An interpolated frame is composed of the processor's best guess as to what should be there, based on the contents of each of the true frames.
At CES, LCD TV makers announced new models with 240Hz refresh rates, which are designed to reduce motion blur even further. There are two distinct methods used by different manufacturers to arrive at that number. I've reviewed one 240Hz display, the Sony KDL-52XBR7, which uses MEMC again to basically double the 120Hz process described above--so for each "true" frame there are three interpolated frames. Samsung also uses MEMC to get to 240Hz.
LG, Toshiba, and Vizio, on the other hand, use what's called "scanning backlight" technology. Instead of interpolating a second time, it uses MEMC once to get to 120Hz, in combination with a backlight that flashes on and off very quickly, to claim a 240Hz refresh rate. Notably, Toshiba used the careful phrase "240Hz effect" at its press conference to describe the scanning backlight method, although we doubt the distinction will filter down to the product packaging. I haven't reviewed any displays that use this method yet, so I can't speak to whether one method is better than the other.
Despite having reviewed only one HDTV with 240Hz, however, I'm fairly confident that the feature, regardless of how it's implemented, is not worth waiting for on its own, unless you're the kind of highly sensitive viewer who already perceives motion blur in 120Hz models.
Personally, I have a difficult time perceiving motion blur in standard 60Hz LCDs, even in side-by-side comparisons with 120Hz LCDs or plasmas, unless I'm using specialized test material. (I'm talking about motion blur only here, not "smooth" dejudder processing, which is separate from refresh rate and quite easy to perceive.)
According to that test material, the 240Hz Sony XBR7 did in fact reduce motion blur significantly compared with 120Hz displays, so I'm willing to believe claims that 240Hz is less-blurry than 120Hz. In case you're wondering, the XBR7 delivered between 900 and 1,000 lines of motion resolution, which matches the result of a typical plasma.
That compares with 500-600 lines for a standard 120Hz model like the Sony KDL-52XBR6 and 300-400 lines for a 60Hz LCD. But those results were with test patterns. The real question is whether you actually tell the difference in everyday viewing? For most viewers, the answer is "no."
Hey, maybe I'll be surprised when I do get my hands on more 240Hz TVs and they turn out to be the cat's meow. Anything can happen, but until then I'm not telling anyone to hold out for 240Hz tomorrow when you can get 120Hz (or less!) today.
David Katzmaier reviews HDTVs for CNET. 
And the pixel pitch is perfectly fine as is for 50" HDTVs unless you're sitting two feet in front of it.
The bandwidth required for good video is immense. Studios ALREADY down-grade (by factor of 4, I believe?) to Blu-ray format. The problem is, you can still see artifacts and jumpy video with even with blu-ray on these HD TVs. So the problem is NOT resolution, it's video bandwidth and the sacrifices made for compression. 30fps >> 24fps.
Reducing the hold time is what reduces the blur for people. There is no blur on a display, it is instead on the retina which holds the image around 10ms (this duration varies in people depending on their eyes).
Displays that hold each frame for a short amount of time work better with human vision. So what the LCD makers have been working towards is reducing the amount of time the each frame needs to be held.
The older Samsung 81f model with a scaning backlight had a 60hz panel and a scanning backlight. The backlight is turned on from 8.3ms then is off 8.3ms. What LG is doing with their claimed "480hz" model is turning on the backlight for 4ms then turning it off for 12ms. To pull this off they are more than doubling the amount of LED clusters.
Plasma and the OLED display from Sony have a hold time of 8.3ms. So LG has created a display that is 100% faster in generating each frame. The hold time for a display is the most crucial aspect for a display to remain razor sharp to human vision. The lower the better.
so why are some companies "frame doubling" to build interstitial frames when it's not necessary?
im wondering the same thing...
so if companies are claiming 240hz by "frame doubling" or backlighting, whatever technology they may use, is there some sort of true 240hz?
Not all material has a high frame rate. Most DVD and Blu-Ray disc based movies are encoded at 24p (24 frames). This stems from the fact movies are filmed at 24 frames per second. The standard display operates at 60hz. So 60 into 1000 ms (1000 milliseconds in a second) ='s 16.67ms. So each frame on a 60hz display is based on 16.6ms timing.
24 frames multiplied by 16.6ms ='s 398.4ms worth of frame time. That means there is 600ms worth of frame time left. What happens is each frame ends up being repeated twice. If they didn't do that, the display would show 24 frames and the other 36 non-existent frame would be black. Since black non-frames produce zero light, the display would look half as bright.
If you turn on the frame interpolation option, instead of repeating the same frame twice, the TV creates a new frame that is an approximation.
video = 30 fps
lcd = video x 2 = 60
right eye = 60
left eye = 60
updates necessary for both eyes is 60 + 60 = 120
to be able to apply the 120 smoothness effect that David Katzmaier already approves of you would have to double that, hence 240.
120 is also necessary to reach a balance between video @ 30 and film @ 24. 120 is where you reach a common multiple of updates per second to satisfy both. This one of the main reasons film based material exhibits the motion blur effect more than video (with the possible exception of sports).
30 x 4 = 120
24 x 5 = 120
you can apply the same concept from the previous layout to see why 240 would also be good for 3D based movies as well.
Yeah, I know 3D is a ways off. We still haven't seen a set standard for the glasses. But, we're seeing more and more movement on it. There's even a new push for a 3D bit in this years Super Bowl. Coke did a 3D commercial several years back. They uses a different trick for the 3D based on the effect where one eye receives a slightly darker images than the other. When objects are in motion moving from one side (light to dark) it appears to be on a different plane (3D effect) than objects standing still. The entire Coke commercial was a guy chasing a vending machine from the left side of the screen to the right in every shot. It worked because we're preconditioned to this editing effect. Once he stopped the effect went back to 2D. This had the bonus though that if you didn't have the glasses (if I remember right only one eye had a dark lens, the other was clear) then you saw a regular image. You just didn't the "effect" of 3D, but the commercial was not truly in 3D. So, it will be interesting to see what this years 3D bit will be. It's a 90 sec commercial for Monsters vs. Aliens.
With 3D movies and games, it'll be equivalent to your left eye watching a video feed, your right eye watching another. Although it'll be one with alternating the frames so every other one is seen by your left eye, then right eye, et cetera.
Hence, even if the video is only at 24, 30, or 60fps, you'll need to double it to show frames to BOTH eyes. And if you game at 60fps, suddenly 120Hz is required to prevent jutter. Then introduce limitations of LCD tvs, and to prevent blur 240Hz is suddenly reasonable and useful.
"The problem is that with LCD, some viewers can perceive motion blur in fast-moving objects on standard 60Hz models (motion blur like this isn't an issue with plasma or other display types, whether 60Hz or otherwise, because they use different methods to create the illusion of motion)."
I find this a bit misleading.
The common denominater between displays is that they all generate frames, even though they use different technology to do so.
What determines the illusion of motion (having a razor sharp image during fast moving scenes) is the length of time each frame is "left on" or "held". A CRT which is known as impulse display are really good at displaying motion because each frame is only held for a short period of time.
However, I think the "Hz" will be over most consumers head, and over most salespeoples' head as well. The typical shopper will probably get erroneous information thrown at him on the sales floor.
I had a friend that actually bought the Sony KDL-52XBR7, and when we were watching the set for the first time at his house he kept on saying that he was seeing distortions. He would pause, rewind, and play the scene again from his PVR to show me what he saw. Honestly, I couldn't see anything wrong and thought the set looked really clear and blur free. But it bugged him so much he actually returned the Sony and bought the 50" Pioneer Kuro plasma. He's really happy now and I do like the Pioneer's picture, but he still bugs me about now seeing the distortions.
I guess it really depends on the person because I still think the Sony looked really really sharp playing HD.
The larger the panel, the worse the picture. That is still the way it is and always will be it seems. Even in the same model range, my Sharp 52" LCD is far inferior to the same design 32" LCD. The 52" could be 240Hz and the picture would still be lacking?
HOW MUCH OF A PROBLEM IS IT TO HAVE PLASMA IN SUCH A ROOM?
Also CRT is faster than the current OLED models despite the fast switching times of the pixels. It all comes down to how long a display has to "hold an image" before it is bright enough to be useable.
The electron gun generates each frame with enough brightness very quickly. The light generated in Plasma, LCD, and OLED isn't as bright as an electron gun in a CRT.
So Plasma, LCD, and OLED have to hold each frame for a longer duration to get a bright enough frame generated.
A great example of the next great step is the LED lighting solution demonstrated from LG, the 480hz will equal the speed of a CRT. I'm sure Samsung will have something similar soon. All they really need to do is double the amount of LED clusters.
As far as Plasmas go, the 480hz sub-fields have nothing to do with how fast each frame is created. Plasma Sub-Fields serve the purpose of creating a grey scale image. The light generated by the plasma only comes in one level, so the more fields they assign the finer the gradations will be. Then the phosphors add the actual color.
Most plasmas utilize 8 subfields for each frame. 8 x 60 frames = 480 sub-fields
A Pioneer plasma utilzes 14 subfields for each frame. 14 x 60frames = 840 sub-fields
With more sub-fields the Pioneer can create a finer detailed grey scale image. It has nothing to do with creating a grey scale image (black & white frame) faster.
There is a lot of talk of 3D tv standards out there.
I have Read 240hz is what they are shooting for the 3D formats
They would like 240hz TV's, so it can process 2 Video streams @ 120hz per Eye, so there's no eye fatigue when viewing 3d.
... I may be wrong but I am pretty sure I have also come across articles that stated the original 120hz TV's were using 3:2 pull down and not 5:5 so the number of interpolated frames created were far less then the newer TV's even on 120hz Displays.
I thought the whole argument concerning even 120hz was a joke. Even the lowly 1080i sets show full progressive frames every 60th of a second. My answer is simple to all the people who "know" they see blurring.
It's simple, I just ask if they see blurring at the theatre. Movie theatres run films at 24 fpm. It's possible some of the newer digital theatres use more modern electronics to double the frame rate, but a double is just that. Since human perception runs in the low 20's, you don't see blurring at the theatre. As a result, you're certainly not going to see blurring on a television running double the speed of human perception unless it's a really bad TV.
Most people I've met, who claim to see motion blur, are usually watching a very large screen and sitting too closely. They're actually seeing blur all the time, not just during motion. HDTV is pretty much a medium for 42 inch sets; when you start blowing that size up, pixels start to show as do artifacts. On my Olivea 42 1080i, you can stick your nose against the screen and not see one dot, or any crawling. On my 52 1080p set, you can. On my brothers 65 inch, it's not very pretty at all. You must sit way back for that to look clean.
Even if you look at 1080p vs. 1080i. All p does is double the frame again, thereby playing the same frame 4 times instead of 2; achieving the blistering rate of 4 x's human perception. How silly, anything to get the public to buy their sets over and over again.
Just look to computer gaming as your proof. The excepted frame rate to play any first person shooter is 30 fps. At that speed, gameplay is smooth. The video card companies, much the way as HDTV have made cards that can play these games at over 100fps. That speed has messed up game graphics so much, that many games today have built in frame limits so the cards can't over run them. (Call of Duty being one) To stress these cards today, they use huge LCD displays that no one would use. Imagine sitting a foot away from a 27 inch panel?
In other words: HDTV and computer gaming hit the point of diminishing returns long ago; now they have to use gimmicks to sell.
Many don't realize the correlation between LCD televisions and LCD computer monitors. LCD TV's lagged in advancement because the work being done was only being done on computer monitors. When computer monitors came of age, so to speak, and the bugs were out of them; then LCD televisions were viable.
I mention this because the most important spec of an LCD monitor, is never mentioned concerning TV's and it crucial to this blurring argument. And that's panel response time. LCD monitors, at first, were terrible gaming monitors for this reason. With response times of 24ms (milliseconds) they would blur and tear when playing an action game. Once they achieved 8 to 10ms, they were ready to be used for gaming. This didn't happen overnight.
For those not familiar: Response time is the time it take a pixel to go from grey to white and back to grey. Some manufacturers fudge these numbers because there is no standard. Example, if someone claims to have a response time of 3ms, it usually means they're just measuring grey to white, and not back to grey. To be fair, those are really 6ms monitors. But, 6 is a GREAT number just the same.
Since LCD televisions are the same types of panels, it logical to assume response time is just as crucial to them, as it is for computers. You will nary see a response time spec. for a TV. Is this on purpose? Perhaps.
Needless to say, if you have a cheap television and it does really blur, (no matter the manufacturer) it's far more likely that it's a cheap panel with slow response times, more then it would ever be frame rate.
- by sapper6 March 31, 2009 11:26 PM PDT
- Ok, here's the skinny for the non-technical people. I just bought a Phillips 47 inch, 1080P, 120hz T.V.
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- by caprich96 May 7, 2009 9:29 AM PDT
- you are like me i feel the better features cost more money, my girl bought a tv 60 rate it looks amazing and everything but i will put 900 more to get the gorgeous sony bravia z series 46 inc model 5100 with 240 rate and 10 bit rate for video and i also want to get te blue rate. i saw a movie in a blue rate spider man i saw it on best buy and it looks like you are in the movies just with 120 rate i can imagine how it will look with a 240 and the sony blue rate to match my tv im so excite that i will get the newer TV when it is available :) You have a nice TV by the way
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- by deecee May 21, 2009 12:59 PM PDT
- Hey, guys, since you are so into high refresh rate, I have a CRT Computer monitor with 200Hz refresh rate for cheap, trade you for a 60H LCD panel.
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Showing 1 of 2 pages (51 Comments)I messed with the settings while watching the new James Bond film in Blu Ray with a 120hz capable hdmi cable. Phillips calls it Dynamic Range Motion (120hz). When switched off, it looks like a normal movie in high def (still gorgeous). When turned on it looks more life-like. I can explain this in layman's terms. One way to describe it is that the movie looks more like a home video. But not bad quality like a home video, but more like you're there. If you have ever watched a reality show, it's like that, compared to a normal movie polish. Or another way to describe it, for lack of better term, is that has a soap opera look. When people and objects move it looks like it does in real life. At first I didn't like it. I was so used to the old HD, that I resisted first. After watching the newest Quantam Solace on Blu-Ray, a few times; a couple in 60hz, and a couple in 120 hz, I would have to say that I like the 120hz better---way better! My TV has a demo mode where it splits the screen, and shows you the two. But this demo fails to show the difference. It's two confusing, the best way is to just switch it on and watch a 2 minute clip, then switch it off and watch the same clip, then back on and you will notice the difference right away after that. The 120hz truly shows more detail, and I for one am glad to have it. Wether or not its worth all that money extra is up for debate. Is it better? Yes--Go to best buy and have them show you a clip first in 120, then in 60, then in 120--trust me you'll see.