LCDs

[vinayb]

what do u guys think is the difference between the refresh rate of a crt monitor and the response time of a lcd? How are they comparable, i.e is 12ms=85Hz, or something like that interms of performance and image quality??

 

[secretanchitman]

i thought that all lcds (most of them at least) have a refresh rate of 60hz. correct me if im wrong.

 

[Parkre]

no, LCDs have refresh rates higher than 60.

LCDs and CRT have refesh rates. The higher the resolution, the lower the refresh rate (which is usually 60).

LCDs 'response time' is just the time it takes for a pixel to go from gray to gray. (white to black, then black to white) . CRTs don't have these response time because they are progressive (the tube in the back).

If you do a forum search, someone who was ranting about the worthlessness of the response time the company gives. He goes into detail to explain his rant. Very informative.

 

[n7]

Technically, LCDs don't even refresh.

It's different technology, so comparing them is difficult.

 

[Suspicious-Teach8788]

Originally posted by: n7
Technically, LCDs don't even refresh.

It's different technology, so comparing them is difficult.

:thumbsup: Exactly. Forget refresh rate. Leave it at 60 and turn on Vsync if ghosting is noticeable.

As for response time, this is far more important in a LCD monitor.

 

[Parkre]

Originally posted by: n7
Technically, LCDs don't even refresh.

It's different technology, so comparing them is difficult.

ahhhh......You are going to confuse him.......😕

different tech...yes
comparable.....YES

 

[BenSkywalker]

12ms ~= 83.33Hz

Pretty much the answer you are looking for is take 1000 and divide it by the latency rating and you get the rough RR equivelant. As stated above though, the latency rating isn't even a remotely good indicator as it only gives you the gray to gray time(gray to green as an example can be much slower).

 

[klah]

CRTs still have latency in response of <1ms.

http://graphics.tomshardware.com/display/20040923/lcd_monitors-07.html

We use the same method here as for rise time. In fact, the human eye is more sensitive to fall time than to rise time. A white object that leaves a "trail" will be more inconvenient than a white object that takes time to illuminate when moving. Based on our observations, certain manufacturers don't hesitate to "pre-load" their pixels at a lower value before any color change. By doing this, they reduce fall time, but to the detriment of rise time.

On our CRT, the fall time, in fact, corresponds to the display's remanence.

GRAPH

Here we measure 825 µs, which remains beyond the capabilities of the best TFT panels. All we have to do is add the rise time and the fall time to obtain the latency time:
Tl = Tf + Tr = 860 µs

 

[ChuckHsiao]

http://forums.anandtech.com/messageview...atid=31&threadid=1664893&enterthread=y

Refresh rate is important for CRTs because the higher the refresh rate, the less energy is given per flash (i.e. each flash doesn't have to be as bright), so there's less eyestrain. For LCDs, however, there is no flicker, so what's important is the response time, which is how long it takes for a pixel to go from one state to another. Response time is very important if you're a gamer, somewhat important if you watch movies on your computer, and not very important if you just use your computer for M$ or web or photo stuff (for photography work, it's better to get monitors that don't compromise on color quality by trying for a super-fast response time). As for how to compare them, it depends on the individual person. Some people don't get bothered by a 60 Hz CRT. Some people (me included) don't get bothered by a 25 ms response time.

A slow (refresh rate) CRT leads to eyestrain. However, a slow (response time) LCD leads to ghosting, which is that images stay on the screen slightly even while the next couple of images are being shown; moving objects look like they have a shadow or ghost trailing them (hence the term).

Yes LCDs have refresh rates too (the refresh rate is how often the image is changed on the monitor). However, it's not a particularly important consideration, since 60 Hz is fast enough that the eyes don't notice the frames changing. So 60 Hz is plenty for LCDs.

 

[xtknight]

In CRTs, the refresh rate is how often the electron gun paints the screen in a second. The LCD's response time is how fast a crystal can change its state. LCD's dont refresh until the picture sent is being changed, hence why they don't flicker. These are different, and 12ms. doesn't mean the LCD can show a full-screen artifact-free screen every 1/83 of a second. It means the crystals can update that fast. Just one frame from another will always have that motion blur though, no matter how slow the frames change. So, this is quite different from the CRT's vertical scan rate...

 

[Velk]

Originally posted by: Parkre

Originally posted by: n7
Technically, LCDs don't even refresh.

It's different technology, so comparing them is difficult.

ahhhh......You are going to confuse him.......😕

different tech...yes
comparable.....YES

They aren't comparable because they are used as a symptom of something else.

CRT refresh rate is how many times the entire screen is drawn each second, LCD refresh rate is an estimate of how long it would take to draw the entire screen as something different.

People use CRT refresh rate as a measure of flicker, which is irrelevant to LCDs because they don't, no matter how slow they are at drawing the screen.

People use LCD refresh rate as a measure of motion blurring, which is irrelevant to CRTs because they don't, no matter how slowly they are refreshing.


Edit : fix broken quoted bold tag

 

[imported_g33k]

Originally posted by: Velk

Originally posted by: Parkre

Originally posted by: n7
Technically, LCDs don't even refresh.

It's different technology, so comparing them is difficult.

ahhhh......You are going to confuse him.......😕

different tech...yes
comparable.....YES

They aren't comparable because they are used as a symptom of something else.

CRT refresh rate is how many times the entire screen is drawn each second, LCD refresh rate is an estimate of how long it would take to draw the entire screen as something different.

People use CRT refresh rate as a measure of flicker, which is irrelevant to LCDs because they don't, no matter how slow they are at drawing the screen.

People use LCD refresh rate as a measure of motion blurring, which is irrelevant to CRTs because they don't, no matter how slowly they are refreshing.


Edit : fix broken quoted bold tag

That sums it up nicely.

 

[Parkre]

I think my post was confusing now that I look at.

I didn't mean for the technology to be comparable, I meant the screens (i.e. quality, blurriness, frame ripping, etc) were comparable (Such as what you descibe). The technology shouldn't be compared, but the end results can be. I am sorry for the confusion, unless I have confuse you even more, then I will shut up. 😎

 

[VIAN]

do the math:

1000 / response time = refresh rate

 

[SonicIce]

with a CRT, you just have the refresh rate. if its 85Hz, you know its refreshing at 85hz. with an LCD, you have the refresh rate, plus you have response times. maybe just use vians formula? sorry i sound stupid im so tired.