High Def Forum
Thank you for visiting. This is our website archive. Please visit our main website by clicking the logo above.

120Hz vs 8 ms

BamaPanda
12-28-2006, 04:14 PM
Wonder if anyone can translate which of these is quicker? I know the Hz has to do with refresh rate - but I have no idea how that would translate in regard to 8 ms.
So the question is ...what refresh rate does a 8 ms. LCD have?
Any idea?

borromini
12-28-2006, 04:31 PM
Why are you bringing this up again? 99% of all consumer HDTVs have only one refresh rate...60Hz. This is the same answer for LCDs with 4ms, 6ms, 12ms, etc., etc.

BamaPanda
12-28-2006, 04:36 PM
The reason is I saw an LCD rated at 120Hz. and i was curious how that might compare with 8 ms.
Is that an OK question?

borromini
12-28-2006, 04:42 PM
Do you have the link to this 120Hz display?

It's not a real question because the two are unrelated...apples to oranges in terms of how a display works. Refresh rate is constant where pixel response time can be affected by what the screen is displaying.

BamaPanda
12-28-2006, 05:14 PM
Not a link yet. Just had some info on new product coming in March. It is a 42" LCD and it is rated at 120Hz. Surely there must be a way to relate this to ms.
Maybe someone will have an idea.

rbinck
12-28-2006, 05:42 PM
It is going to depend on the resolution of the display. It is a matter of figuring out how much time would be available for each pixel with a scan rate of 120Hz. Next it depends on which method the 8ms is measured. Some measure black to white to black and some measure black to white only. Since from one frame to the next the most extreme would be from full off to full on, or vice versa, that would be the method that would be important.

So take 1920 pixels per line X 1080 lines and multiply by 120 and that is how many pixels must change in a second. The reciprocal will be the time per pixel. The response time needs to be this or faster. Of course there may only be 1366x768 pixels, you really didn't say.

BamaPanda
12-28-2006, 06:37 PM
It is going to depend on the resolution of the display. It is a matter of figuring out how much time would be available for each pixel with a scan rate of 120Hz. Next it depends on which method the 8ms is measured. Some measure black to white to black and some measure black to white only. Since from one frame to the next the most extreme would be from full off to full on, or vice versa, that would be the method that would be important.

So take 1920 pixels per line X 1080 lines and multiply by 120 and that is how many pixels must change in a second. The reciprocal will be the time per pixel. The response time needs to be this or faster. Of course there may only be 1366x768 pixels, you really didn't say.

It is 1366x768P. Sounds a bit complex, but that just may be to my non math mind.
So in the 120Hz set 125,890,560 pixels have to change in a second, right? OK, so take the normal 8 ms in a similar 42" LCD @ the same resolution. How would you convert that to Hz? or vice versa?

rbinck
12-28-2006, 06:47 PM
It is 1366x768P. Sounds a bit complex, but that just may be to my non math mind.
So in the 120Hz set 125,890,560 pixels have to change in a second, right? OK, so take the normal 8 ms in a similar 42" LCD @ the same resolution. How would you convert that to Hz? or vice versa?If 125,890,560 pixels must update in 1 second then each pixel will have 7.94ms to update,1second divided by 125,890,560 pixels, it just makes it. For a 1920x1080 @ 120Hz display it would need 4ms pixels!

rbinck
12-28-2006, 06:58 PM
BTW the real value of that display would be if it will receive a 1080p/24 signal. It could display each frame received 5 times thus eliminating judder from film sources. Same with 1080i/30 assuming its 3:2 reverse pull down processor and deinterlacer is accurate.

BamaPanda
12-28-2006, 08:24 PM
BTW the real value of that display would be if it will receive a 1080p/24 signal. It could display each frame received 5 times thus eliminating judder from film sources. Same with 1080i/30 assuming its 3:2 reverse pull down processor and deinterlacer is accurate.
Not sure on that. There are some 768P sets that will receive a 1080P signal, and then reduce it to 768P - is that right? Maybe this is what this will do - don't know yet. I just got a prelim sheet on it.
So there is really no way to figure the refresh rate on a current 8ms. set? I have not seen it in any specs.

borromini
12-28-2006, 08:41 PM
...So there is really no way to figure the refresh rate on a current 8ms. set? I have not seen it in any specs. If you look at the user manuals available online for any major brand sold in North America with 8ms pixel response time, you'll see that they have a 60Hz refresh rate.

Refrigerator
12-28-2006, 08:53 PM
If 125,890,560 pixels must update in 1 second then each pixel will have 7.94ms to update,1second divided by 125,890,560 pixels, it just makes it. For a 1920x1080 @ 120Hz display it would need 4ms pixels!

That's more like 7.94 nanoseconds which is way shorter than the response time of any LCD.

Why would the response times of the pixels be added together? That would mean that each pixel must wait for the previous one to be turned on before it can be activated.

BamaPanda
12-28-2006, 09:23 PM
If you look at the user manuals available online for any major brand sold in North America with 8ms pixel response time, you'll see that they have a 60Hz refresh rate.
Thanks. Apparently I did not look in the right places.
So 120Hz would be 4ms, right? Sounds right. I read that Sharp is coming with a 4ms. screen - so this might be the same thing.

borromini
12-28-2006, 09:34 PM
You seem intent on connecting the two as if one feature must drive the other. Sharp's upcoming model may have a 4ms pixel response time and yet still have a 60Hz refresh rate...they exist today. Or it may have a 120Hz refresh rate and an 8ms pixel response time. One does not drive the other.

BamaPanda
12-28-2006, 10:19 PM
You seem intent on connecting the two as if one feature must drive the other. Sharp's upcoming model may have a 4ms pixel response time and yet still have a 60Hz refresh rate...they exist today. Or it may have a 120Hz refresh rate and an 8ms pixel response time. One does not drive the other.

OK, thats fine. I just seen a prelim and was trying to understand some of the specs a bit more. I am sure when the final specs are ready, it will make more sense.

BrianO
12-28-2006, 10:59 PM
There is no direct relation between refresh rate and pixel response time. The refresh rate simply dictates the maximum reponse time that pixels can have to be compatible.

The refresh rate is the number of times per second that the screen is updated. Each individual pixel is updated the same number of times per second as the screen. So if the screen's refresh rate is 60 Hz then each pixel is updated 60 times per second. As long as the response time of the pixels is faster than 1/60 of a second (16.67 ms), then it is fast enough to be updated at 60 Hz.

To support a 120 Hz refresh rate, the pixels must have a respose time of 8.33 ms or less.

BamaPanda
12-29-2006, 09:06 AM
So to get that 120Hz refresh rate - the pixels would have to be able to respond twice as fast as what we might see in our normal 8ms, 60Hz LCD screen today.
That helps.
Thanks.

ChaosMan1014
12-29-2006, 09:56 AM
f=1/Time
f=1/8ms
f=125Hz

inversley

Time=1/f
Time=1/120Hz
Time=8.33ms

8ms is a faster response time than 120Hz but not by much

borromini
12-29-2006, 10:03 AM
So to get that 120Hz refresh rate - the pixels would have to be able to respond twice as fast as what we might see in our normal 8ms, 60Hz LCD screen today... No, your statement is misleading...did you actually read the math? A more apt description would be: An LCD display with 120Hz refresh rate would have to be able to respond twice as fast as a 16ms, 60Hz LCD. :rolleyes:

rbinck
12-29-2006, 12:32 PM
That's more like 7.94 nanoseconds which is way shorter than the response time of any LCD.

Why would the response times of the pixels be added together? That would mean that each pixel must wait for the previous one to be turned on before it can be activated.My bad. That would describe the response of the driving electronics not each pixel. As was stated before, each pixel would be changed every 1/120th of a second which is 8.3 ms.

BamaPanda
12-29-2006, 01:33 PM
Found a link touting a new 120 hz LCD panel.
http://www.hitachi.us/tv/browse/lcd/lcd/37HLX99.shtml
Looks to be some really new technology that might help LCD with gamers - fast movement in general.

BrianO
12-29-2006, 02:35 PM
So to get that 120Hz refresh rate - the pixels would have to be able to respond twice as fast as what we might see in our normal 8ms, 60Hz LCD screen today.
That helps.
Thanks.

No. The 8ms panels found on today's 60Hz sets are already fast enough to support use at a refresh rate 120 Hz. (8ms < 8.33 ms)

BamaPanda
12-29-2006, 04:21 PM
Still a bit of a mystery to me how the Hitachi can tout a 120 hz panel, because when you go to the manual for that set it is still rated at 60 hz just like everyone elses.
Maybe the answer lies (and I am not an electrical expert nor a math whiz) in the thing I saw when I opened a few other PDF manuals along with the Hitachi manual - that the 60 hz spec seems to relate to electrical power and PC connectivity only. I read nothing that said anything about 60hz having anything to do with the speed of the pixels or the refresh rate.
Looking on the surface it would seem that we have something new with the Hitachi. Actually, I saw the same thing on a larger Samsung, if I recall.

BrianO
12-29-2006, 05:35 PM
Still a bit of a mystery to me how the Hitachi can tout a 120 hz panel, because when you go to the manual for that set it is still rated at 60 hz just like everyone elses.
.

It shows 60 active frames per second but shows an all black frame in between each active frame, so it does refresh the screen 120 times per second. Basically it shows a frame, erases it, shows the next frame, erases it, and so on. In this way each active frame starts with a clean slate rather than "overwiriting" the previous frame, thereby (supposedly) increasing image sharpness in moving images.

To be compatible the pixels must have a response time of less than 1/120 second (8.3 ms), as previously calculated. They must be able to go from black to fully saturated in 120th of a second and then go from fully saturated to black in the next 120th of a second. 8 ms would probably be adequate but 6 ms would be better.

BamaPanda
12-29-2006, 06:19 PM
Looks like Philips has it too.
http://www.digitaltigers.com/s-ips.shtml

nmlobo
12-31-2006, 07:48 AM
So does JVC. They released two 120hz models earlier this year.

BamaPanda
12-31-2006, 07:54 AM
So does JVC. They released two 120hz models earlier this year.
Doesn't seem to have been that much discussion on it. Looks to be a way to bring the LCD panel 'up to speed' with the PDP. It would neat to know if it actually helps in an all around way, color depth and PQ.

borromini
12-31-2006, 10:30 AM
Refresh rate can improve PQ in terms of sharpness, but I highly doubt that it has any affect on color depth.

screntist
01-01-2007, 12:45 PM
Still a bit of a mystery to me how the Hitachi can tout a 120 hz panel, because when you go to the manual for that set it is still rated at 60 hz just like everyone elses.
Maybe the answer lies (and I am not an electrical expert nor a math whiz) in the thing I saw when I opened a few other PDF manuals along with the Hitachi manual - that the 60 hz spec seems to relate to electrical power and PC connectivity only. I read nothing that said anything about 60hz having anything to do with the speed of the pixels or the refresh rate.
Looking on the surface it would seem that we have something new with the Hitachi. Actually, I saw the same thing on a larger Samsung, if I recall.

Yeah, if you see a rating like 100-240V, 50/60Hz . . . . that is definitely not the "Hz" that is being discussed in this topic.

borromini
01-02-2007, 12:42 AM
It's already been noted in a previous post how the Hitatchi achieves a 120Hz rating.

BamaPanda
01-02-2007, 07:37 AM
It's already been noted in a previous post how the Hitatchi achieves a 120Hz rating.
I must have missed that. Link please, if you know it.

borromini
01-02-2007, 11:24 AM
It's not a link, it's the explanation provided in an earlier post (#24) by BrianO.

Rick-F
01-02-2007, 11:46 AM
The reason is I saw an LCD rated at 120Hz. and i was curious how that might compare with 8 ms.
Is that an OK question?

120 Hz is 120 cycles per second. It is a FREQUENCY

8 ms is a duration of time eight thousands of a second or 8 milliseconds.

By the way-- something operates at 120 Hz completes one cycle each 8.333 ms (1 divided by 120)

BobY
01-02-2007, 10:21 PM
An LCD with 120Hz refresh rate still has a long was to go to catch Plasma or CRT even at a 60Hz refresh rate.

The refresh rate really isn't the issue, it's the response time. While an 8mS response time may allow a theoretical 120Hz refresh rate (any slower response time and the picture would never be stable), the image will only be stable for a short period of time. Plasma and CRT response time is under 1mS. The picture stabilizes much faster and remains stable for a much longer time than with LCD and that translates to a sharper picture.

BamaPanda
01-03-2007, 08:05 AM
An LCD with 120Hz refresh rate still has a long was to go to catch Plasma or CRT even at a 60Hz refresh rate.

The refresh rate really isn't the issue, it's the response time. While an 8mS response time may allow a theoretical 120Hz refresh rate (any slower response time and the picture would never be stable), the image will only be stable for a short period of time. Plasma and CRT response time is under 1mS. The picture stabilizes much faster and remains stable for a much longer time than with LCD and that translates to a sharper picture.
I think that earlier post (#24) by BrianO probably helps understand this more than anything. I don't recall seeing anything mentioned about ms speed of the pixels even on Hitachi's site, although it looks to be about 8 ms. Be neat when we get some reviews on 'in plane switching' to see if it really does improve response. Everything I have seen seems to really indicate that it does improve LCD viewing angles pretty dramatically, though.

BobY
01-03-2007, 11:06 AM
Of course it's an improvment for LCD's, that wasn't my point.

Plasma and CRT are still much faster. Since all HD video is either 60Fps, 30Fps or 24Fps, there is no "speed" advantage to a 120Hz refresh rate--60 Hz is fast enough to reproduce the motion perfectly. Having a faster response time will make one *LCD* look better than another *LCD*, but a Plasma or CRT with a 60Hz refresh will have better motion response than an LCD, even with a 120Hz refresh rate and an 8mS response time.

borromini
01-03-2007, 11:21 AM
I've tried several times to make this point that there is no real relationship between pixel response time and refresh rate, but obviously unsuccessful.

BobY
01-03-2007, 11:34 AM
The only relationship is, if the response time is longer than or equal to one screen refresh period, then a faster refresh rate is irrelevant, as the picture won't have stabilized before it gets refreshed with a new image.

It may seem ridiculous to produce a display with a slower response time than one refresh period, but in the earlier days of consumer LCD's this was common and most motion would look blurry. You didn't see a sharp picture until the motion stopped and the picture had a chance to stabilize.

borromini
01-03-2007, 11:38 AM
As you noted, it's been a few years since the pixel response time couldn't keep up with refresh rate. I was certainly making my point in regards to current and future iterations. I just don't know why the OP is still hung up on this.

BamaPanda
01-03-2007, 03:48 PM
The OP is raising a 5 year old, and the thinking at times is cloudy.

maicaw
02-08-2007, 02:23 PM
According to the Sharpusa tech guy I talked to today - this Sharp LC52D92U set is a significant improvement over the older 52" 4ms 60Hz refresh set being sold by Costco -Item # 399052 - Model LC-60C52U($300 off coupon available later this month) and amazon - model# LC-52D62U http://www.amazon.com/Sharp-Aquos-LC-52D62U-1080p-HDTV/dp/B000HKJKBS/sr=8-1/qid=1170961269/ref=pd_bbs_1/102-5690407-8776158?ie=UTF8&s=electronics http://www.smartbrief.com/news/cea/industryBW-detail.jsp?id=40D65F2A-ED66-419B-A964-30F1E99A9F4F&brief=CEA
AQUOS Widescreen 1080p HDTV Series (models LC42D92U, LC46D92U, LC52D92U and LC65D93U)
The new widescreen series of Full HD1080p HDTV AQUOS Liquid Crystal Televisions, available in 42, 46, 52, and 65inch screen sizes, features the topoftheline version of Sharp's proprietary Advanced Super View panel, the most advanced LCD panel in the world. This panel technology enables an incredible 15,000:1 Dynamic Contrast Ratio for deep blacks and crisp picture quality; Fine Motion Advanced technology for 120 Hz Frame Rate Conversion; enhanced Quick Shoot video circuitry for faster pixel response time of 4ms; and wide viewing angles of 176 degrees, so users can view the proprietary 5wavelength backlight system that provides a wider color spectrum to achieve deeper, more vivid reds and greens than was previously possible. Additionally, all units in this series include three HDMI(TM) inputs, two HD component terminals, and one DVII input, all of which are compatible with 1080p signals from Bluray and other new devices, in addition to RS232C for custom installations. The entire series features Full HD 1080p (1920 x 1080) resolution for an unparalleled highdefinition experience. These newly redesigned models are available in a stunning piano black finish with detachable bottom speakers and include a detachable table stand. Also joining these new Full HD 1080p AQUOS LCD TVs is a 65inch model that shares the same advanced features as the D92U line but offers a varied design of highgloss piano black finish with fixed bottomplaced speakers. The LC42D92U will be available in April for a Manufacturer's Suggested Retail Price (MSRP) of $3,499.99 and the LC46D92U and LC52D92U and will be available in January for MSRPs of $4,199.99 and $5,299.99, respectively. The LC65D93U will be available in March for an MSRP of $10,999.99. - and AVS forum thread on this Sharp LC52D92U 120hz refresh unit is http://www./avs-vb/printthread.php?t=735728&page=51&pp=60

Fiber5
11-24-2011, 08:16 PM
The reason is I saw an LCD rated at 120Hz. and i was curious how that might compare with 8 ms.
Is that an OK question?

120Hz means 120 blinks per second or one (1) blink in 0.008 second. Divide 1/120=0.008 which is 8millisecond or 8ms :))

Simple math )))

120Hz is 8ms ( two different notations for the same frequency)
simmilarly if you divide 1/60 = 0.016666 = 16ms
Or 1/240 =0.00416666= 4ms

Here we go: 60Hz or 16ms,
120Hz or 8ms,
240Hz or 4ms,

BrianO
11-25-2011, 03:53 PM
120Hz means 120 blinks per second or one (1) blink in 0.008 second. Divide 1/120=0.008 which is 8millisecond or 8ms :))

Simple math )))

120Hz is 8ms ( two different notations for the same frequency)
simmilarly if you divide 1/60 = 0.016666 = 16ms
Or 1/240 =0.00416666= 4ms

Here we go: 60Hz or 16ms,
120Hz or 8ms,
240Hz or 4ms,

You are responding to a thread that has been dead for almost 5 years. And your conclusion is wrong as far as the context of the thread is concerned because you are comparing apples to oranges.

Screen refresh rate and pixel response time are two different issues. The former is the rate at which the screen is updated; the latter is the speed with which the pixels can respond to the TVs attempt to update it. The only connection between the two issues is that the pixel response time must be fast enough to respond in the time made available to it by the refresh rate. To eliminate blurring the response time of the individual pixels must be less than 1000/(screen refresh rate in Hz). And because not all of the pixels in the screen have exactly the same response time (there is always some variation), the average response time must be significantly less than 1000/Hz. While theoretically a refresh rate of 8 ms is fast enough to support a screen refresh rate of 120 Hz, in practice it will still lead to a significant amount blurring: a pixel response time of 6 ms or faster will produce much better results.