100mhz or response time? Which is more important?

Marino · 18-02-2008, 14:51

I'm close to buying my first high-definition LCD TV but I'm confused by the difference between 100mhz TVs versus response times in elimination ghosting on fast moving subjects and giving a smoother picture. A friend of mine returned a 50mhz TV because of ghosting and replaced it with a 100mhz model which seemed to solve the problem for him. I'm toying between a Panasonic model and the Sharp Aquos range. The 32 inch Panasonic has great reviews with its 100mhz but I prefer the look of the Sharp Aquos range although it is only 50mhz but has a fast 6ms response refresh rate. Will the fast 6ms response rate eliminate ghosting and do the same job as the 100mhz Panasonic models or are they 2 entirely different concepts? If they are, which is the better option to focus on? Am I barking up the wrong tree here in comparing the 2 options? I'm looking for a TV that will give me smooth movement on fast action on screen. I don't want to spend about £800 and find I've bought the wrong TV. Can anyone help to explain the differences in these 2 concepts? Thanks.

chrisjr · 18-02-2008, 15:41

For a kick off it is 50Hz and 100Hz. These figures relate to the field rate of the TV, which is an entirely different thing to response rate.

A TV picture comprises 25 pictures (frames) per second. For reasons that need not be gone into here each frame is divided into two fields - 50 fields per second hence 50Hz. One has all the odd numbered lines and one the even numbered lines. A CRT (old fashioned) TV scans the tube twice per frame first with the odd lines then the even lines. That concept doesn't really apply to LCDs which can display an entire frame in one go.

The difference between 50 and 100Hz sets is that a 100Hz set repeats every frame twice. Which is claimed to reduce flicker.

The response time of a LCD basically defines how quickly the pixels in the picture can change state. There may be a linkage in that a 100Hz set has to display twice as many pictures per second as a 50Hz set but even so that only requires a 20mS refresh rate (in very crude terms anyway). So anything faster than that is going to be OK for normal viewing. The field rate (50 or 100hz) does not by itself indicate how good a set is. Response rate may be a better guide.

Chris Simon · 18-02-2008, 16:03

Quote:

Originally Posted by chrisjr

For a kick off it is 50Hz and 100Hz. These figures relate to the field rate of the TV, which is an entirely different thing to response rate.

As far as I'm aware, 100Hz in relation to LCD TVs refers to the frequency at which the backlight flickers, as opposed to being a steady light. This is claimed to reduce motion blur on LCD sets as the pixels are only illuminated when they are "fixed" and not in the intermediate stages of changing state.

The OP has a valid question really - at what point does a fast pixel response time outweigh advantages of 100Hz.

The situation you've described is for CRT TVs, where the frames are repeated twice in order to provide a flicker-free image for those people that can perceive a 50Hz flicker. But flciker is not the same as motion blur, which is what the 100Hz on LCD TVs is aimed at solving.

Chris Simon · 18-02-2008, 16:12

Having said that though...

http://www.reghardware.co.uk/2007/05...p_lc32_lcd_tv/

This says that this TV has a 100Hz refresh rate, which gives it a response time of 4ms, which is indeed puzzling. Perhaps the reviewer has misunderstood what the 100Hz refers to, or perhaps the term "refresh rate" is misleading? Surely it refers to the "refresh rate" of the backlight not the refresh rate of the frames.

bobcar · 18-02-2008, 16:17

Hilarious mistake 100mHz - that's a frame every 10 seconds, we might see some judder.

A fast response can make a difference when compared to an LCD that has one that is too slow.

More important than either of these factors is the signal processing involved especially de-interlacing and upscaling. neither of these has an easy measurement though so reading reviews and seeing for yourself is the only sensible thing to do - forget the specs it's the picture that counts.

bobcar · 18-02-2008, 16:36

Quote:

Originally Posted by Chris Simon

Having said that though...

http://www.reghardware.co.uk/2007/05...p_lc32_lcd_tv/

This says that this TV has a 100Hz refresh rate, which gives it a response time of 4ms, which is indeed puzzling. Perhaps the reviewer has misunderstood what the 100Hz refers to, or perhaps the term "refresh rate" is misleading? Surely it refers to the "refresh rate" of the backlight not the refresh rate of the frames.

You've misunderstood what refresh rate is for an LCD. The backlight will flicker as it's a fluorescent but this is not the refresh rate.

The refresh rate for an LCD is how often the screen is updated if it's updated at 100 Hz the LCD will "work out" what the intermediate frames would have been so for instance a ball moving across the screen will be in a position between the two frames. How well this is done determines how good the final picture is - it can be worse.

P.S. The reviewer has it wrong as well, the refresh rate is not the same as the response time which is how long the lcd shutters take to get into position.

Chris Simon · 19-02-2008, 13:00

Quote:

Originally Posted by bobcar

You've misunderstood what refresh rate is for an LCD. The backlight will flicker as it's a fluorescent but this is not the refresh rate.

Yeah, but I thought there was technology that used a non-fluorescent backlight, i.e. LEDs, which can be turned on and off instantly, at 100Hz, to only illuminate the pixels when they have "settled", so you don't see the intermediate stages of the pixels responding.

I hadn't heard of 100Hz technology that actually interpolates the intermediate frames, but that still would only work with a really fast response time to reduce motion blur because the screen would have to respond twice as fast???

[EDIT] seems it's actually very complicated and both definitions are valid! http://www.behardware.com/articles/6...afterglow.html and
http://www.highdefforum.com/showthread.php?t=39118

infiniteloop · 19-02-2008, 13:16

Quote:

Originally Posted by bobcar

Hilarious mistake 100mHz - that's a frame every 10 seconds, we might see some judder.

no, it's 4million frames per second at 25fps. I'd be happy with that I reckon

(1mhz = 1 million cycles per second)

chrisjr · 19-02-2008, 13:31

Quote:

Originally Posted by infiniteloop

no, it's 4million frames per second at 25fps. I'd be happy with that I reckon

(1mhz = 1 million cycles per second)

Wrong

m (lower case) means milli, ie one thousandth
M (upper case) means Mega ie one million

So 100mHz means one hundred thousandths of a cycle per second. Or one tenth of a cycle per second or one cycle per ten seconds.

Subtle difference, but in some circumstances could make a shed load of trouble - imagine if a chemist making up a prescription got his m and M mixed up

infiniteloop · 19-02-2008, 13:53

Quote:

Originally Posted by chrisjr

Wrong

m (lower case) means milli, ie one thousandth
M (upper case) means Mega ie one million

So 100mHz means one hundred thousandths of a cycle per second. Or one tenth of a cycle per second or one cycle per ten seconds.

Subtle difference, but in some circumstances could make a shed load of trouble - imagine if a chemist making up a prescription got his m and M mixed up

to be fair, the OP used all lower-case, so he could have meant either

(both wrong, obv., and i typed it wrong in my last sentence)

18-02-2008, 14:51	#1
Marino Forum Member Join Date: Aug 2005 Posts: 12	100mhz or response time? Which is more important? I'm close to buying my first high-definition LCD TV but I'm confused by the difference between 100mhz TVs versus response times in elimination ghosting on fast moving subjects and giving a smoother picture. A friend of mine returned a 50mhz TV because of ghosting and replaced it with a 100mhz model which seemed to solve the problem for him. I'm toying between a Panasonic model and the Sharp Aquos range. The 32 inch Panasonic has great reviews with its 100mhz but I prefer the look of the Sharp Aquos range although it is only 50mhz but has a fast 6ms response refresh rate. Will the fast 6ms response rate eliminate ghosting and do the same job as the 100mhz Panasonic models or are they 2 entirely different concepts? If they are, which is the better option to focus on? Am I barking up the wrong tree here in comparing the 2 options? I'm looking for a TV that will give me smooth movement on fast action on screen. I don't want to spend about £800 and find I've bought the wrong TV. Can anyone help to explain the differences in these 2 concepts? Thanks.

18-02-2008, 15:41	#2
chrisjr Forum Member Join Date: May 2004 Location: Reading Posts: 27,916	For a kick off it is 50Hz and 100Hz. These figures relate to the field rate of the TV, which is an entirely different thing to response rate. A TV picture comprises 25 pictures (frames) per second. For reasons that need not be gone into here each frame is divided into two fields - 50 fields per second hence 50Hz. One has all the odd numbered lines and one the even numbered lines. A CRT (old fashioned) TV scans the tube twice per frame first with the odd lines then the even lines. That concept doesn't really apply to LCDs which can display an entire frame in one go. The difference between 50 and 100Hz sets is that a 100Hz set repeats every frame twice. Which is claimed to reduce flicker. The response time of a LCD basically defines how quickly the pixels in the picture can change state. There may be a linkage in that a 100Hz set has to display twice as many pictures per second as a 50Hz set but even so that only requires a 20mS refresh rate (in very crude terms anyway). So anything faster than that is going to be OK for normal viewing. The field rate (50 or 100hz) does not by itself indicate how good a set is. Response rate may be a better guide.

18-02-2008, 16:03	#3
Chris Simon Forum Member Join Date: Mar 2000 Location: Snowdonia Posts: 2,725	Quote: Originally Posted by chrisjr For a kick off it is 50Hz and 100Hz. These figures relate to the field rate of the TV, which is an entirely different thing to response rate. As far as I'm aware, 100Hz in relation to LCD TVs refers to the frequency at which the backlight flickers, as opposed to being a steady light. This is claimed to reduce motion blur on LCD sets as the pixels are only illuminated when they are "fixed" and not in the intermediate stages of changing state. The OP has a valid question really - at what point does a fast pixel response time outweigh advantages of 100Hz. The situation you've described is for CRT TVs, where the frames are repeated twice in order to provide a flicker-free image for those people that can perceive a 50Hz flicker. But flciker is not the same as motion blur, which is what the 100Hz on LCD TVs is aimed at solving.

18-02-2008, 16:12	#4
Chris Simon Forum Member Join Date: Mar 2000 Location: Snowdonia Posts: 2,725	Having said that though... http://www.reghardware.co.uk/2007/05...p_lc32_lcd_tv/ This says that this TV has a 100Hz refresh rate, which gives it a response time of 4ms, which is indeed puzzling. Perhaps the reviewer has misunderstood what the 100Hz refers to, or perhaps the term "refresh rate" is misleading? Surely it refers to the "refresh rate" of the backlight not the refresh rate of the frames.

18-02-2008, 16:17	#5
bobcar Forum Member Join Date: Sep 2004 Posts: 14,718	Hilarious mistake 100mHz - that's a frame every 10 seconds, we might see some judder. A fast response can make a difference when compared to an LCD that has one that is too slow. More important than either of these factors is the signal processing involved especially de-interlacing and upscaling. neither of these has an easy measurement though so reading reviews and seeing for yourself is the only sensible thing to do - forget the specs it's the picture that counts.

18-02-2008, 16:36	#6
bobcar Forum Member Join Date: Sep 2004 Posts: 14,718	Quote: Originally Posted by Chris Simon Having said that though... http://www.reghardware.co.uk/2007/05...p_lc32_lcd_tv/ This says that this TV has a 100Hz refresh rate, which gives it a response time of 4ms, which is indeed puzzling. Perhaps the reviewer has misunderstood what the 100Hz refers to, or perhaps the term "refresh rate" is misleading? Surely it refers to the "refresh rate" of the backlight not the refresh rate of the frames. You've misunderstood what refresh rate is for an LCD. The backlight will flicker as it's a fluorescent but this is not the refresh rate. The refresh rate for an LCD is how often the screen is updated if it's updated at 100 Hz the LCD will "work out" what the intermediate frames would have been so for instance a ball moving across the screen will be in a position between the two frames. How well this is done determines how good the final picture is - it can be worse. P.S. The reviewer has it wrong as well, the refresh rate is not the same as the response time which is how long the lcd shutters take to get into position.

19-02-2008, 13:00	#7
Chris Simon Forum Member Join Date: Mar 2000 Location: Snowdonia Posts: 2,725	Quote: Originally Posted by bobcar You've misunderstood what refresh rate is for an LCD. The backlight will flicker as it's a fluorescent but this is not the refresh rate. Yeah, but I thought there was technology that used a non-fluorescent backlight, i.e. LEDs, which can be turned on and off instantly, at 100Hz, to only illuminate the pixels when they have "settled", so you don't see the intermediate stages of the pixels responding. I hadn't heard of 100Hz technology that actually interpolates the intermediate frames, but that still would only work with a really fast response time to reduce motion blur because the screen would have to respond twice as fast??? [EDIT] seems it's actually very complicated and both definitions are valid! http://www.behardware.com/articles/6...afterglow.html and http://www.highdefforum.com/showthread.php?t=39118

19-02-2008, 13:16	#8
infiniteloop Forum Member Join Date: Feb 2006 Location: London Posts: 5,149	Quote: Originally Posted by bobcar Hilarious mistake 100mHz - that's a frame every 10 seconds, we might see some judder. no, it's 4million frames per second at 25fps. I'd be happy with that I reckon (1mhz = 1 million cycles per second)

19-02-2008, 13:31	#9
chrisjr Forum Member Join Date: May 2004 Location: Reading Posts: 27,916	Quote: Originally Posted by infiniteloop no, it's 4million frames per second at 25fps. I'd be happy with that I reckon (1mhz = 1 million cycles per second) Wrong m (lower case) means milli, ie one thousandth M (upper case) means Mega ie one million So 100mHz means one hundred thousandths of a cycle per second. Or one tenth of a cycle per second or one cycle per ten seconds. Subtle difference, but in some circumstances could make a shed load of trouble - imagine if a chemist making up a prescription got his m and M mixed up

19-02-2008, 13:53	#10
infiniteloop Forum Member Join Date: Feb 2006 Location: London Posts: 5,149	Quote: Originally Posted by chrisjr Wrong m (lower case) means milli, ie one thousandth M (upper case) means Mega ie one million So 100mHz means one hundred thousandths of a cycle per second. Or one tenth of a cycle per second or one cycle per ten seconds. Subtle difference, but in some circumstances could make a shed load of trouble - imagine if a chemist making up a prescription got his m and M mixed up to be fair, the OP used all lower-case, so he could have meant either (both wrong, obv., and i typed it wrong in my last sentence)

DS Forums

100mhz or response time? Which is more important?