Consumer Reports (a magazine that seems to be written by experts, that is until they dabble in a field you might already be an expert in) is saying that 240 Hz will reduce motion blur over 120 and even more over 60 Hz FPs. They even performed what appears to be a credible experiment to prove this. But then they also state that old-style interlaced CRTs have less motion blur than even the 240 Hz FPs, and don't explain that.

I am skeptical, to say the least. It seems that even if an image is moving, it still is captured as a still image at either 30 or 60 fps, and no higher, which means that 240 Hz could not really produce more unique images. Not only that, but human perception, even under the best of circumstances, is not supposed to be able to detect flicker above 60 Hz, making numbers higher than that imperceptible overkill.

If you combine the truth of that physics with the fact that there is no screen blanking with FPs (some image always is constantly displayed) and the fact that a 240 Hz display will display (at 60 Hz) four identical images sequentially compared to a 60 Hz display displaying one image for 4 times as long (which seems to be effectively the same thing as far as perception is concerned), regardless of whether there is motion or not, I just simply fail to understand why 240 would have any advantage.

My best guess is that no one can explain that to me to anyone's satisfaction, but I am willing to become educated on the subject and learn why CR thinks 240 Hz displays have an edge.

Please chime in if you have an explanation (please disregard pulldown and judder issues, which are a separate discussion).

TIA.

120/240 maybe a gimmick indeed. I have yet to read sum1 going, "wow, 240hz totally worth$ it!"

...which means that 240 Hz could not really produce more unique images.

they make the unique images by interpolating frames.

...human perception, even under the best of circumstances, is not supposed to be able to detect flicker above 60 Hz, making numbers higher than that imperceptible overkill.

flicker aside, its been proven we can see images a little above 200fps.
images with durations longer than that will blur progressively more.
so i'd guess any blur in a 240hz set is due to imperfect implementation.


..there is no screen blanking with FPs...a 240 Hz display will display (at 60 Hz) four identical images sequentially compared to a 60 Hz display

they blank the screen or interpolate and sometimes both. either way, the reduced frame duration reduces blur.
you may opt to repeat the same frame, but like you said that won't have much effect on blur :)

If you are familiar with the concept of display “hold-time” and how it relates to refresh rate and blur then you will understand the theory behind 240Hz LCD and how it compares to CRT.

Aside from the blur caused by pixel response, the displays duty cycle (effective or intrinsic) along with the refresh rate determine the time each frame is displayed on your retina which in turn determines the amount of retinal blur (aka - hold type blur).

Assuming a signal is 60Hz with a frame period of 16.7ms, below is a ranking of display types according to the respective hold times (time period the display is emitting light per frame)-The longer the hold time the worse the perceived motion blur.

Display - Hold Time
PMOLED - microseconds
CRT - 1-2ms (depending on phosphor decay)
LCD 240Hz (interpolated) - 4.18ms
Plasma - 4-8ms (depending on phosphor decay and output level)
LCD 120Hz (interpolated) - 8.33ms
AMOLED - 16.7ms
LCD 60Hz - 16.7ms

http://www.avsforum.com/avs-vb/showthread.php?p=14832288#post14832288
http://www.avsforum.com/avs-vb/showthread.php?p=16104519#post16104519
http://www.avsforum.com/avs-vb/showthread.php?p=15098327#post15098327
http://www.avsforum.com/avs-vb/showthread.php?p=13883623#post13883623

The "blur" that people percieve while watching a fast moving sport and complain about doesn't exist on the display. When the eye is tracking fast moving objects and each frame has a long "hold time" the image is getting smeared on the eye.

The way a CRT operates interacts well with the human visual system as it tracks moving objects on the screen. Each pixel is only being shown for a very brief period of time.


The companies that manufacture LCDs can't simply decrease the hold time without any consequence. If you lower the hold time from 8.3ms to 4.18ms the brightness of the screen is going to be decreased.

Most LCD displays are 60hz based, which equals 60 frames at 16.67ms. It is basic math, 60 * 16.67ms ='s 1002ms or 1 second.

All a 120hz LCD is doing is taking taking the 16.67ms frame "on" time and cutting it in half to 8.3ms "on" and 8.3ms "off". So 120 frames at 8.3ms.

One solution is to lower the hold time, but to make up for the lack of "on time" of frames being shown they use interpolation to generate a fake frame. So instead of one frame "on" for 8.3ms and "off" for 8.3ms, they show the original frame for 4.18ms, then have 4.18ms off, then interpolate a fake frame and show that for 4.18ms, then have 4.18ms off.


LCDs with Rear-Lit LED lights can improve their brightness by putting more light clusters into the display. As they put more light clusters, they can decrease the hold time. Of course putting in more LED lights increases the cost of the display.

LCDs that are Edge-Lit LED can lower their hold time as LEDs become brighter and the actual LCD panels become more light effcient. The new UV2A panel technology by Sharp is an example of this.

I was under the impression that the real issue was with movies. Movies are filmed at 24 fps, and a 60 hertz TV has to show some frames longer than others, while a 120 hertz TV can show each frame for the same duration.

That was my understanding, is it totally off base?

I was under the impression that the real issue was with movies. Movies are filmed at 24 fps, and a 60 hertz TV has to show some frames longer than others, while a 120 hertz TV can show each frame for the same duration.

That was my understanding, is it totally off base?


In its discussion of the effectiveness of 240 Hz implementation, they specifically use tennis and video games as the type of programming where motion blur can be most easily seen.

The other points worth noting are that not all sets with "240" showed the reduced motion blur. CRs, "A few Samsung and Sony TVs we tested with 240 HZ enabled showed virtually no motion blur, a breakthrough for LCDs".

The reference to CRTs is of no importance.

If you are familiar with the concept of display “hold-time” and how it relates to refresh rate and blur then you will understand the theory behind 240Hz LCD and how it compares to CRT.

Aside from the blur caused by pixel response, the displays duty cycle (effective or intrinsic) along with the refresh rate determine the time each frame is displayed on your retina which in turn determines the amount of retinal blur (aka - hold type blur).

Assuming a signal is 60Hz with a frame period of 16.7ms, below is a ranking of display types according to the respective hold times (time period the display is emitting light per frame)-The longer the hold time the worse the perceived motion blur.

Display - Hold Time
PMOLED - microseconds
CRT - 1-2ms (depending on phosphor decay)
LCD 240Hz (interpolated) - 4.18ms
Plasma - 4-8ms (depending on phosphor decay and output level)
LCD 120Hz (interpolated) - 8.33ms
AMOLED - 16.7ms
LCD 60Hz - 16.7ms

http://www.avsforum.com/avs-vb/showthread.php?p=14832288#post14832288
http://www.avsforum.com/avs-vb/showthread.php?p=16104519#post16104519
http://www.avsforum.com/avs-vb/showthread.php?p=15098327#post15098327
http://www.avsforum.com/avs-vb/showthread.php?p=13883623#post13883623

There's one thing I don't understand. Newer models of Samsung LCDs can allow you to turn off interpolation and use strictly "blur reduction" What exactly is that?

I'm no expert on these newer technologies but I can say that when seeing demos of 120HZ and 240HZ sets, they look almost like watching a faster PAL film, where the image is sped up unnaturally. It doesn't seem fluid and in fact seems more jarring than the blurring itself. Of course, that may just be the way my eyes perceive it, since I am still a HD CRT user.

There's one thing I don't understand. Newer models of Samsung LCDs can allow you to turn off interpolation and use strictly "blur reduction" What exactly is that?

I imagine that it would be the television running a 60hz signal at 240hz without adding in the extra frames that create the soap opera effect. A movie would still move like a movie, but would be protected from unwanted motion blur.

As for the main topic, for people who don't watch sports or play video games, there probably is no pay off as they wouldn't be using content fast enough to make the TV blur. From my experience playing FPS or racers on a 60hz LCD is miserable and I'm glad that the push for 3D tech is getting 120hz and 240hz sets made.

I think it mostly has to do with everyone's eyes. Everyone see's things differently. When I went and got my LN52a550, I looked at the 60 and 120 tv sets. One of the tests I had the sells man do was to pause the TV during a fast motion spot. I heard from these forums that was a good way of checking for motion blur. In all honesty, with my eye's, I could not tell the difference between a 60 & 120. So I saved a few hundred and bought the 60. Even today, like during a NASCAR race, I will puase the race as the cars are going by and at that speed, do not see any blur or even while they are racing. Movies are just great and have no regrets buying the 60.

I'm no expert on these newer technologies but I can say that when seeing demos of 120HZ and 240HZ sets, they look almost like watching a faster PAL film, where the image is sped up unnaturally. It doesn't seem fluid and in fact seems more jarring than the blurring itself. Of course, that may just be the way my eyes perceive it, since I am still a HD CRT user.

Because it enhances (some might say unnaturally) real life and the way your retina itself blurs. It definitely takes a while to get used to and isn't for everyone. Some people even have an adverse physical reaction to the effect. Although most can retrain their brain to accept the motion. Watch sports for a while and it does become indispensible.

I think it mostly has to do with everyone's eyes. Everyone see's things differently. When I went and got my LN52a550, I looked at the 60 and 120 tv sets. One of the tests I had the sells man do was to pause the TV during a fast motion spot. I heard from these forums that was a good way of checking for motion blur. In all honesty, with my eye's, I could not tell the difference between a 60 & 120. So I saved a few hundred and bought the 60. Even today, like during a NASCAR race, I will puase the race as the cars are going by and at that speed, do not see any blur or even while they are racing. Movies are just great and have no regrets buying the 60.

My friend could play first-person-shooters (video games) like: Quake, Far Cry, Half Life for countless hours, on an early LCD no less. For me, just looking at the fast moving blur, flicker, judder-filled screen for even a few minutes made me physically ill; I would literally have to lie down. My sensitivity was so intense that the effect could last for up to an hour.

I eventually discovered that you can retrain the brain's visual interpretation by changing the center of focus slightly. While our eyes all operate on the same basic principles, our brains are as unique as fingerprints in the way we interpret images. And the eyes are a major part or extension of that malleable brain.

One of the tests I had the sells man do was to pause the TV during a fast motion spot. I heard from these forums that was a good way of checking for motion blur. In all honesty, with my eye's, I could not tell the difference between a 60 & 120. So I saved a few hundred and bought the 60.

they should look exactly the same when paused...that test will only tell you how blurry the original source frames were.
120/240hz tackles the additional blur that occurs when these frames are presented to your eye in dynamic sucession.
call it eye-induced motion blur or whatever, but there is a definite right and wrong way to present a sequence of images without blur.
if the source frames are blur-free (say a video game) its easy to see this type of blur, which i guess C.R. noticed.

[The correct motion blur and judder test is to place the two images side-by-side. Pausing won't be a demonstration of motion blur, but it might show some visual compression from a live cable feed... especially in fast moving scenes with hardly any static action.

There's one thing I don't understand. Newer models of Samsung LCDs can allow you to turn off interpolation and use strictly "blur reduction" What exactly is that?

This is probably adjusting the duration of each frame or "hold time".


The DPI Titan Dual Ultra DLP projector also lets users make adjustments like this. They call it "fast frame". It can be adjusted anywhere from 1-16ms. You lose light output as you decrease the duration of each frame.

Chalk it up as another band-aid on a cancer for LCD.

James

This is probably adjusting the duration of each frame or "hold time".


The DPI Titan Dual Ultra DLP projector also lets users make adjustments like this. They call it "fast frame". It can be adjusted anywhere from 1-16ms. You lose light output as you decrease the duration of each frame.

Are you referring to some kind of strobe duration?

I've been curious about this myself. My theory was that rather than generate the interpolated frames evenly, they generate very similiar (very subtle interpolation) frames within the source frame's duration. This would reduce retinal retention while not filling in the differences so much as to produce "soap opera effect".

It is indeed "all in your head." All in my head, too.

I just posted an article on this with some images to help explain the concept.

240 Hz and Beyond (http://www.hemagazine.com/240Hz)

great article,

At 60 times per second, this is above your flicker-fusion threshold, and as such appears smooth.

There is a point where individual images shown rapidly stop being individual images and become smooth motion: flicker fusing to motion.


this being the main premise, flicker (strobing) technically is not related to smooth motion, which can be attained at frame rates well below flicker-fusion (75hz minimum). flicker is simply "the frequency at which an intermittent light stimulus appears to be completely steady to the observer" to quote wiki. the 3:2 explanation was simpler.

for those who want to get rid of the jutter of 3:2 (me!) but don’t want motion interpolation (hey, me again!) you can do 5:5 pulldown, and just repeat each film frame five times. So you get the benefit of the faster refresh and additional frames without the ugliness artifacts side effects of motion interpolation.

probably important to some, you lose the benefit of motion blur reduction with this option.

I noticed the difference between 60 and 120. The first time I realize it was when the guy showed me the text running by on the demo tvs at fry's. From there I couldn't really see much advantage to 240 or LED. I went with the Samsung LN46A650 and haven't looked back since. I saved a bunch of money on my car insurance by switching to Geico... oh wait. lol

It is indeed "all in your head." All in my head, too.

I just posted an article on this with some images to help explain the concept.

240 Hz and Beyond (http://www.hemagazine.com/240Hz)

That's an excellent article, thanks Geoff!

BTW nice site but the reviews desperately need measurements!

240hz pfft. lame

480hz Sony LCD
or
600hz Plasma

sports and movies look like garbage on 120hz and 240hz units.

Chalk it up as another band-aid on a cancer for LCD.

James

Or you could see it as a limitation of stagnant film and video production, at 24fps and 60fps respectively. Just like high definition exposes the weaknesses of a standard definition source on plasma, LCD etc., or digital exposes the weaknesses of an analog source.

240hz pfft. lame

480hz Sony LCD
or
600hz Plasma

sports and movies look like garbage on 120hz and 240hz units.

480Hz and 600Hz, they both seem like specs based on marketing speak to me.

480Hz and 600Hz, they both seem like specs based on marketing speak to me.

The purpose of publishing them is marketing, but they are real specs. Not sure how they make use of those extra frames, though.

The real point of all this is not how many frames you can jam into a second, but how how little time the display spends transitioning between frames (blur). Response time is far more useful for this (actually xrox's post above lays this out most excellently) but again, it's subject to testing methods and marketing spin.

Or you could see it as a limitation of stagnant film and video production, at 24fps and 60fps respectively. Just like high definition exposes the weaknesses of a standard definition source on plasma, LCD etc., or digital exposes the weaknesses of an analog source.


Funny, my plasma looks fine with 24 and 60 sources. It's my LCD that goes from bad to bad with comparable media and standard and 120 tech.

James

Funny, my plasma looks fine with 24 and 60 sources. It's my LCD that goes from bad to bad with comparable media and standard and 120 tech.

James

So so True, which is why I refuse to play the industry game with LCD's. Which is why I am going 600hz 1080p 60p 24p compatible Plasma. Its like take your most Expensive LCD with every best feature. Now make the picture look better better colors black image overall, They subtract $1,000 bucks and you have a Plasma. Its all about BEST image and video quality and I will not compromise pay more and get worse image quality with and LCD.

Its all about BEST image and video quality and I will not compromise pay more and get worse image quality with and LCD.

Never before has "Beauty is in the eyes of the beholder" been more relevant than in response to your post. To you a Plasma is the better picture, but to my eyes 1080P 120Hz LCD has an extremely attractive, slightly surrealist three dimensional quality to it. At first glance it imparts a "soap opera/video" effect, but after your eyes "adjust" (just as if you were coming from outdoors into a dark theater) you begin to notice the incredible clarity and detail of 120Hz.

This TV (http://www.bestbuy.com/site/Insignia%26%23174%3B+-+46%22+Class+/+1080p+/+120Hz+/+LCD+HDTV/9554519.p?id=1218131143082&skuId=9554519&st=insignia%2046%20inch%20120%20hz) had an amazing picture, when viewing HD (SD was only so-so), but I had to return it due to an A/V sync problem.

Bluephase from Samsung is supposed to be 240hz native, so four times that of 60hz standard lcds. In that UV2A video interview with Sharp, a rep for the company talks of microsecond reponse times with the new panel.

My bravia doesn't have any extra blur that I know of. At least, I'm not seeing it, which works for me.

If it's true with these new panels from Samsung and Sharp, motion blur and viewing angles will be the same as plasma.