Waveform 09A Motion Blur and 120hz LCD Frame Rate Processing

Educational column for understanding video systems
HD Library
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Waveform 09A Motion Blur and 120hz LCD Frame Rate Processing

Postby HD Library » 24 Sep 2008, 22:14

This is not a complete article and is therefore posted here in HD Library until I can reach a final conclusion and version regarding the ins and outs of motion related artifacts. Most of this content is based on observed experience living with an LCD for over 60 days. At this time the main purpose is to provide a reference point for LCD reviews and consumers seeking relevant information. A great starting point is an article from Rodolfo, <a href="http://www.hdtvmagazine.com/articles/2008/01/lcd_specs_playing_with_your_eyes.php">LCD Specs Playing with Your Eyes</a>.


Motion blur is being used as a generic term to describe a multitude of different and independent motion artifacts that any display technology can suffer from or that any capturing system creates before ever getting to a display. The only reason it has come to the forefront is due to the unique sample and hold properties of direct view LCD display imaging, the very high contrast ratios direct view LCD provides along with detail motion blur, an artifact all displays can suffer from yet is far more degrading with direct view LCD and therefore considered a unique artifact of direct view LCD.

Motion Blur, Your Eyes and Frame Rate
The human visual system is sensitive to frame rate and based on testing peaks out at 60 frames per second. This is the magic number where most folks simply can

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Postby HD Library » 25 Sep 2008, 15:29

Edit - additional content

Add to that your Viewing Distance and Contrast Ratio
Using the HD critical viewing distance of 3 screen heights the artifacts from 24 and 30 frame content was very apparent if not irritating. In the upstairs system though normal viewing distance for the 46

perfectinght
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Postby perfectinght » 26 Sep 2008, 07:56

:idea:
Turning down the bias lighting as provided by the Mitsubishi did improve on this aspect but do you really want to forsake all that dynamic range?

I'll assume you meant to say back lighting, rather than" bias lighting." :)

Best regards and beautiful pictures,
Alan Brown, President
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A Lion AV Consultants Affiliate

"Advancing the art and science of electronic imaging"

Roger Halstead
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Motion blurr and 120 Hz refresh?

Postby Roger Halstead » 27 Sep 2008, 02:12

Well, it's not exactly a 120 or even 60 Hz refresh rate the way they do it with LCDs.

I tend to agree on a number of points, but disagree with the motion blur and even 30 Hz refresh. I've run 22" monitors on my computers for some time now and even with high speed action see no flicker. That is with each frame being sharp when I step through them. The only time I've ever seen flicker was when there were fluorescent lights in the room and these screens have a very short refresh time. The same is true with our now, old (2 years) Samsung 40" LCD even sitting up close I've never noticed flicker or artifacts with motion. OTOH I have seen it just go out to lunch and freeze up for a few frames on a few occasions. From college physics classes we determined that the persistence of the average human eye (in class) was such that *normally* it sees 30 fps and faster as smooth motion even when the individual images are sharp. You don't need a slow shutter speed to blur the image to make the transition between frames look smooth.

Now having said all that, I can understand where the way LCDs refresh it can lead to images that are either not smooth or appear to be in several places at once...or parts of the image have moved farther than others. I've not seen it, but it should be possible. OTOH for minimizing the possibility of such happening I do thing the 120 Hz refresh is a good idea. However, where are you going to get any use out of it. Don't the broadcast stations and satellites still stick with the 30 CPS/Hz refresh. At least DISH has gone to 1080P where the best OTA is 1080I and cable seems to lower the resolution to squeeze in more channels. OTOH so do the local PBS stations <:-))

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Postby Richard » 29 Sep 2008, 21:34

There are a variety of perceptual optical illusions and artifacts that varies with each persons ability to perceive them. I see strobing and flickering from 24 and 30 frame sources rather easily and it is not display sensitive for me; from film to digital display technologies.

It may take some education to see an artifact. Film judder is something I easily ignore and had difficulty observing. The first time it was pointed out to me I saw it plain as day but at that time, 6 years ago, I also blocked that education since there was no affordable video solution. With our new native 24 frame displays it is an artifact I can stop mentally blocking!

Ignorance is bliss!

What you have confirmed and needs to be drilled in over and over is for each viewer to test an LCD themselves to find out if they recognize any of these motion problems rather than performance reviewers, authors and sites making a blanket statement that LCD has motion problems and buyers should avoid them.

If I want to go looking for LCD motion artifacts I can easily see them but after 60 days of casually watching TV it was rare for a motion artifact to show up with a big sign saying "here I am"...

Please read the Rodolfo article to understand how 120hz processing is applicable to 24 and 30 frame sources!
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Postby Richard » 22 Dec 2010, 09:48

A burning question has been whether or not plasma is better than LCD due to all the known problems with LCD. Dr. Raymond Soneira of Displaymate took on this task with Widescreen Review publishing his findings under the title of LCD-Plasma Display Technology Shoot-Out. This is a great educational series covering video standards with an unexpected outcome.

Part 1 was published September 2009, volume 18, number 5, issue 142
Dr. Soneira covers differences in the technologies based on color space, gamma, brightness, contrast ratio and black luminance. Much revolves around viewing angle since this is an LCD problem. What I did find missing was discussion on how plasma is limited in light output, dynamically scaling light output based on picture content to avoid over driving the power supply. Unlike LCD or other lamp based technologies for front projection, with plasma you must calibrate grayscale and gamma with a window pattern due to this anomaly. Our old CRT technology suffered from the same and was calibrated in similar fashion.

Part 2 was published November 2009, volume 18, number 7, issue 144
Dr. Soneira covers LCD response time measuring motion blur ending with a comparison of calibrated LCD versus calibrated plasma displays with real world imaging in a controlled viewing environment for the shoot-out.

The Shoot-Out was fully operational for several months, so we had lots of time to study and compare all of the effects, and over that period of time we had several dozen people come by to see it running and evaluate the effects themselves, including industry experts, manufacturers, engineers, reviewers, journalists, and ISF instructors, all of which are trained observers.


While many of the issues with LCD were found to be true, under controlled conditions Dr. Soneira found LCD doing just fine right next to a plasma.

1) LCD response time specifications are a useless measurement of image performance and there was no visually detectable difference between LCD displays with different response times.

While there was considerable motion blur in the moving test patterns, motion blur was simply not visually detectable in real live video content during our extensive side-by-side testing. Whenever blur was detected in live video, we always found it to be in the source content.


2) Motion processing is best left turned off. You can ignore all the hype about 120, 240 or 480hz motion processing bells and whistles.

3) There was no discernable difference between LCD and plasma with real world video content

It’s also very easy to think that you see blur when you are looking at lots of fast action on a single TV, and a lot of it undoubtedly has its origins in the human visual system. It just doesn’t stand up to the extensive side-by-side testing that we’ve described here.


And in typical video standards fashion that rails against the marketing and hype...

if you stick with the mid to top tier models from the reputable brands, you should ignore Response Time specifications, not worry about LCD motion blur, and don’t spend extra for 120hz or higher refresh rates, strobed LED backlighting, or advanced motion blur processing.


Due to changes in how manufacturers market their products this statement needs some perspective. The key here is to not concentrate on these bells and whistles. Yet you may get them anyway when buying mid to top tier models, in which case, turn those features off if video standards is your viewing goal!

Bottom line: Plasma still retains one advantage, viewing angle for both color accuracy and maximum dynamic range. For the singular videophile desiring an experience based on video standards LCD is comparable. The plasma advantage affects only other viewers because they will not be sitting in your seat. Therefore, if you are buying an LCD, go to the store and reproduce the viewing angles for your family and guests so you can see the difference for yourself on the model you are thinking about purchasing. I bet you find these differences are acceptable. If not check other models while you are there since it is the panel technology that affects this. If you are still not satisfied or simply desire every angle be color accurate with maximum dynamic range then buy a plasma!
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Postby Richard » 22 Dec 2010, 09:50

It appears this series from Dr. Soneira is available on the Displaymate website!

Part 1
http://www.displaymate.com/LCD_Plasma_ShootOut.htm

Part 2
http://www.displaymate.com/LCD_Response ... ootOut.htm
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Postby Rodolfo » 23 Dec 2010, 14:07

Would anyone be interested in getting my wife’s 60” plasma Kuro Pioneer Elite in exchange for letting her have an incredible looking LCD?

I know you may feel shortchanged so I am willing to compensate for your kindness.

Best Regards,

Rodolfo La Maestra


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