Anybody know why LCD's suffer from motion blur?

[WaddyP]

The biggest problem with LCD's is because the pixels can't turn on & off as fast as a plasma's can. It doesn't matter how fast the refresh is or how many (120, 240) hertz if the pixels can't respond as fast. I think the LCD manufacturers try to keep this info (pixel turn on/off speed) hushed so they can go on fooling the public as to (supposedly) how superior the spec's are for LCD. I believe in "seeing is believing", not just spec's on paper! If the picture doesn't look good who cares what the spec's are.

[rbinck]

Originally Posted by WaddyP

The biggest problem with LCD's is because the pixels can't turn on & off as fast as a plasma's can. It doesn't matter how fast the refresh is or how many (120, 240) hertz if the pixels can't respond as fast. I think the LCD manufacturers try to keep this info (pixel turn on/off speed) hushed so they can go on fooling the public as to (supposedly) how superior the spec's are for LCD. I believe in "seeing is believing", not just spec's on paper! If the picture doesn't look good who cares what the spec's are.

They advertise the pixel response time which is a measure of the turn on/off time. The newer ones can get down to the 2ms range, but that is still much slower than plasmas. However, most people don't notice the pixel response blur on the very fast LCDs anymore. If someone does, they would probably be better off with a plasma.

But even with a plasma there can still be motion blur in the source. Additionally, watching broadcast programming there will be macroblocking in fast motion. For me those are more annoying because I know they are the fault of the delivery system, not my TV.

[xrox]

Slow pixel response is not the main cause of LCD blur issues as some have suggested. The correct answer is that LCDs suffer from ‘hold-type’ blurring. This is a tough concept to understand and explain but I have had a lot of practice doing so over the years so here goes .

In real life, objects that are in motion move continuously in an analog fashion. And our eyes track those objects in an analog fashion as well. However, a display cannot render motion this way. Displays must render motion by displaying a sequence of still images in rapid enough succession that fools our eyes into perceiving smooth motion.

Now here is where the problem occurs. When watching a display, our eyes will track a moving object on the display in a continuously analog fashion. But as I said before the display can only display still images one after the other. This creates a conflict because your eyes will still be moving while the image (each frame) is stationary. The stationary frame literally draws a blur onto your moving retina (similar to moving a camera with the shutter open).

The longer each unique frame is displayed on the screen, the longer the blur onto your moving retina. And LCD has the worst issue with this because LCD has a 100% duty cycle (LCD displays the frame for 100% of the refresh period). If you compare the time each frame is displayed on each technology you can see it matches exactly with motion blur reputation (best to worst):

PMOLED - microseconds
CRT - 1-2ms (due to phosphor decay)
Plasma – 4-6ms
LCD (120Hz + interpolation) – 8.3ms
AMOLED (60Hz) – 16.7ms
LCD (60Hz) – 16.7ms

To combat this phenomenon in display technology, the time each unique frame is displayed must be minimized. This can be accomplished in many different ways depending on display capabilities:

1 - Reduce the duty cycle to below 100%
- Flash each frame for only an instant (like CRT, SED, FED, and PMOLED)
- Use weighted pulses to compile a frame like Plasma displays
- Increase the refresh rate and add black frames in between signal frames
- Scan the backlight in LCD displays

The drawback of course is that flicker is introduced

2 – Increase the refresh rate and add interpolated frames

The drawback/benefit of course is that motion judder is significantly changed

[rbinck]

Hmmmm... What about films in the theaters? Aren't they pretty close to the 100% duty as well?

[Loves2Watch]

Originally Posted by xrox

Slow pixel response is not the main cause of LCD blur issues as some have suggested. The correct answer is that LCDs suffer from ‘hold-type’ blurring. This is a tough concept to understand and explain but I have had a lot of practice doing so over the years so here goes .

In real life, objects that are in motion move continuously in an analog fashion. And our eyes track those objects in an analog fashion as well. However, a display cannot render motion this way. Displays must render motion by displaying a sequence of still images in rapid enough succession that fools our eyes into perceiving smooth motion.

Now here is where the problem occurs. When watching a display, our eyes will track a moving object on the display in a continuously analog fashion. But as I said before the display can only display still images one after the other. This creates a conflict because your eyes will still be moving while the image (each frame) is stationary. The stationary frame literally draws a blur onto your moving retina (similar to moving a camera with the shutter open).

The longer each unique frame is displayed on the screen, the longer the blur onto your moving retina. And LCD has the worst issue with this because LCD has a 100% duty cycle (LCD displays the frame for 100% of the refresh period). If you compare the time each frame is displayed on each technology you can see it matches exactly with motion blur reputation (best to worst):

PMOLED - microseconds
CRT - 1-2ms (due to phosphor decay)
Plasma – 4-6ms
LCD (120Hz + interpolation) – 8.3ms
AMOLED (60Hz) – 16.7ms
LCD (60Hz) – 16.7ms

To combat this phenomenon in display technology, the time each unique frame is displayed must be minimized. This can be accomplished in many different ways depending on display capabilities:

1 - Reduce the duty cycle to below 100%
- Flash each frame for only an instant (like CRT, SED, FED, and PMOLED)
- Use weighted pulses to compile a frame like Plasma displays
- Increase the refresh rate and add black frames in between signal frames
- Scan the backlight in LCD displays

The drawback of course is that flicker is introduced

2 – Increase the refresh rate and add interpolated frames

The drawback/benefit of course is that motion judder is significantly changed

Sorry to inform you of this but plasmas are in the microsecond arena not the slower millisecond area as is LCD.

[xrox]

Originally Posted by Loves2Watch

Sorry to inform you of this but plasmas are in the microsecond arena not the slower millisecond area as is LCD.

Why are you sorry? The data I provided is accurate, you just misunderstood. The data is the measurement of "HOLD TIME" and is not a measurement of "RESPONSE TIME". This is explained in the post clearly. The number 4-6ms hold time for PDP comes from the amount of time light is emitted from the pixel during one refresh of 16.7ms.

And BTW, the notion of plasma displays having microsecond response times is obtained from cherry picking data points IMO.

Plasma displays have a microsecond response time in the sense that the gas can be discharged very quickly and in short bursts.
Plasma displays also have microsecond response times with regards to the rise and fall time of the blue phosphors
Plasma displays also have microsecond response times with regards to the rise time of the red and green phosphors
However, Plasma displays have millisecond response times with regards to the fall time of the red and green phosphors.