# How can 60 frames per second be displayed with 25ms pixel ..

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Anonymous

Video gurus,

I need your comments on the following:

While shopping for LCD-TV, I saw the specs:

1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
switched on/off 40 times per second?

2. 1280x720p at 60 frames - means 60 frames per second (
progressive)

Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
from?

Anonymous

It does not. A good 60 frame progressive is about 15ms

With 25ms you may get smearing, especially if this were used also as a
computer monitor

Richard R.

"reader" <medusamouth@yahoo.com> wrote in message
> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?
>
> 2. 1280x720p at 60 frames - means 60 frames per second (
> progressive)
>
> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?
>
Anonymous

> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?
>
> 2. 1280x720p at 60 frames - means 60 frames per second (
> progressive)
>
> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?
>

Well, most of the LCD TVs I've seen in stores are clearly not
displaying interlaced signals in an interlaced way... they're
interpolating it to pseudo-progressive, usually at a resolution of
only 768 lines. The result is that the image is blurred in both space
and time: it's never as sharp as a non-LCD HDTV, and it also smears
when something moves. So the answer as to how it can display 60 FPS
is: it just does it badly.
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Anonymous

> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?
>
> 2. 1280x720p at 60 frames - means 60 frames per second (
> progressive)
>
> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?
>

I'd like to hear the answer as well. The numbers don't add up.
Anonymous

paul-NOZPAM@paulkienitz.net (Paul Kienitz) writes:
>
>> Video gurus,
>>
>> I need your comments on the following:
>>
>> While shopping for LCD-TV, I saw the specs:
>>
>> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
>> switched on/off 40 times per second?
>>
>> 2. 1280x720p at 60 frames - means 60 frames per second (
>> progressive)
>>
>> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
>> from?
>>
>
> Well, most of the LCD TVs I've seen in stores are clearly not
> displaying interlaced signals in an interlaced way... they're
> interpolating it to pseudo-progressive, usually at a resolution of
> only 768 lines. The result is that the image is blurred in both space
> and time: it's never as sharp as a non-LCD HDTV, and it also smears
> when something moves. So the answer as to how it can display 60 FPS
> is: it just does it badly.
>
I agree -- I was just comparing DLP vs. LCD of similar size... LCD had

John
Anonymous

On 17 Nov 2004 19:32:24 -0800, reader <medusamouth@yahoo.com> wrote:
> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?
>
> 2. 1280x720p at 60 frames - means 60 frames per second (
> progressive)
>
> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?

I have a 19" HDTV ready LCD monitor and 27" widescreen HDTV LCD TV.

The 19" has 25ms response time, but I do not notice any ghosting when
playing games like Doom3 @ 60fps, when playing DVDs, or even Quake3 with
high contrast background. Changing shades does not take as long as
complete fade from white to black. The only time any ghosting was
noticeable was if there was white text scrolling on black background on
the OTA digital set top box. Not sure if that was source or display
issue, since I do not notice ghosting with PC video.

My 27" LCD TV has 16ms response time, so it should not have any problem
with 60fps 720p content. But I have only had it a few days and have not
really noticed if anything is ghosting. It certainly beats my old 20"
Panasonic CRT TV in overall viewing and sharpness.
Anonymous

A lot of video source material is taken from film which is only 24 frames
per second.
International video from PAL TV is 50 fields per second.

Where video motion is too rapid for the LCD to handle it is simply
blurred-smeared over. In the HDTV system when there is a great deal of
complex rapid motion producing too much data, it will be 'macroblocked'
over. (The resolution will be decreased for a moment.)

"reader" <medusamouth@yahoo.com> wrote in message
> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?
>
> 2. 1280x720p at 60 frames - means 60 frames per second (
> progressive)
>
> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?
>
Anonymous

"reader" <medusamouth@yahoo.com> wrote in message
> Video gurus,
>
> I need your comments on the following:
>
> While shopping for LCD-TV, I saw the specs:
>
> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
> switched on/off 40 times per second?

Response time refers to how long it takes the pixel to respond to a
command. Every pixel will show you the change up to 25 MS later than it was
told to change (IE: the "live" show you are watching is not really live; it
is delayed up to 25 MS inside the display).

> 2. 1280x720p at 60 frames - means 60 frames per second ( progressive)

720p is usually 30 frames per second, not 60 FPS. Interlaced is almost
always 60 FPS.

> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
> from?

You are dividing apples by oranges and then subtracting bananas.
Response time is (effectively) a measure of the delay between action and
reaction, and not much else.

Bottom line: the faster the response time, the better the picture.
Anonymous

On Fri, 19 Nov 2004 16:13:10 -0600, That Guy <someone@somewhere.com> wrote:
>
>
> "reader" <medusamouth@yahoo.com> wrote in message
>> Video gurus,
>>
>> I need your comments on the following:
>>
>> While shopping for LCD-TV, I saw the specs:
>>
>> 1. 25ms pixel response time - means ( 1000/25 = 40) - a pixel can be
>> switched on/off 40 times per second?
>
> Response time refers to how long it takes the pixel to respond to a
> command. Every pixel will show you the change up to 25 MS later than it was
> told to change (IE: the "live" show you are watching is not really live; it
> is delayed up to 25 MS inside the display).
>
>> 2. 1280x720p at 60 frames - means 60 frames per second ( progressive)
>
> 720p is usually 30 frames per second, not 60 FPS. Interlaced is almost
> always 60 FPS.

You have that backwards. Interlaced does odd lines in 1/60 sec and even
lines in 1/60 sec, 1/30 second total (30 fps). Progressive does the full
image (all lines) in 1/60 sec (60 fps).

>> Where does extra ( 60 - 40 = 20) 20 times switching of the pixel come
>> from?

Instead of the liquid crystals becoming clear or opaque within the 0.0167
sec between 60 fps frames, it takes 0.025 sec if the response time is 25
ms. So you may end up with slight ghosting for 0.008 sec (a rather short
period of time). But it will partially change within that time, so you
would have to have very sensitive eyes to notice it. I just got a DVD
player that can upconvert to 720p on DVI (60 fps) and on my 16 ms LCD TV
there is no ghosting.
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