Question on LCD response times

[shytfaced]

Article

"A 16ms LCD monitor corresponds to 63 images per second, while 12ms is equivalent to 83 images a second."

Does this mean if you have an LCD with a 16ms response time, even if it runs at 75-85hz, to the naked eye we'll only really be able to see 63 frames per second?

 

[Synful Serenity]

In a perfect world, what you say would be true, since frame rate in seconds is determined by dividing 1 sec by the amount of time it takes to draw 1 frame. So we would have 1000ms/12ms=83.33 fps. But this assumes the 12ms rating is uniform across all pixel color transitions. This isn't so, unfortunately.

You should look at the 12ms rating as more of an average than an absolute value. This number is subject to both estimation error and differing standards of measurement between manufacturers. This is why a 16ms screen can have less blur than a competing "12"ms. An LCD pixel works by twisting to block out light. However, it is not able to just twist and retwist as needed....Once it is in the process of twisting, if it has to allow more light through, which would be an "untwist", it must first twist all the way first, then untwist completely, before it can twist to some point before where it was originally. This is similar to how a flag must first be raised to the top before being lowered to half staff. Since the travel would be the longest in the middle of its twist, which are also middle colors, then these halftone shifts, as they are called, take the longest, much longer than the usual black-white color change that is used to obtain the rating. It can take a screen up to 50ms or more in these cases.

So what does this mean? In order for a screen to be absolutely blur-free, there can't be any trace of the previous frame into the next. Since the time for different color transitions varies, to be guaranteed 16ms in 100% of operating conditions means that the slowest possible color change would take 16ms. If we conservatively accept that the slowest color change takes 3 times longer than the screen's rated capability (it can take longer), then to have at least 16ms, you would need a 5ms screen (to account for those times when slower midtone shifts take 15ms, still under 16ms). Some people won't notice the slowdown, but others will since everyone's ability to perceive motion is different. Therefore, your LCD could probably accept a Hz rating of 100, or whatever you want...however, the actual frame rate will be whatever the LCD is capable of displaying. And in the case of 16ms, if you have fast eyes, you might be surprised to notice you may be getting quite less than 60fps.

 

[shytfaced]

So basically from what you're saying, running a game on an LCD is gonna be noticably slower than on a CRT? Everyone seems to be concerned with image quality and ghosting when it comes to gaming on an LCD, but I'm concerned about the actual speed of the game.

When playing on my CRT, at 12x10 the refresh rate is 60hz, and at 10x7 it's 85hz. (and from what i've been told even if you're running 100fps, if your refresh rate is 75hz, you'll only be able to see 75fps) So would playing on an LCD be like the difference between playing at 12x10 and 10x7 on my CRT?

Like if I had the same game running on the LCD and CRT side by side both at the same resolution and 75hz, all image quality and ghosting bullshit aside, would they appear to be running at the same speed?

 

[Synful Serenity]

That is what I'm saying, but that might not necessarily be the case. From a technical standpoint, an LCD screen will be slower, but as I said, everyone's eyes are different. Some people can see fast movement more than others. Motion blur can also be caused by your eyes, and in that case an LCD's blur will be masked by their own eyes' tendency to blur fast motion. That is if you have "slow" eyes. For people with fast eyes that can track faster movement, they will be able to notice the difference. However, some even still might not care. It's all a matter of personal preference.

You are correct in saying that your fps can only be as fast as your refresh rate. The difference here, however, may be more than the difference you see between the two settings on your CRT. At 75Hz, an LCD will appear to be running at the same speed in terms of onscreen events happening at the right time, but there will be some lag in rendering frames which manifests as blur. At 60fps, you might be able to detect some degree of motion blur which isn't there on the CRT at the same settings. As long as there isn't outright ghosting with visible afterimages, many LCD gamers don't seem to mind. But many do....it would be a good idea to test out some LCDs at Circuit City or a friend's house. It's kind of ironic to me though, that the blurriest I've seen an LCD is dragging an open window around the screen! And playing Diablo 2 with my souped up Barbarian was a fright - I had to come to a complete stop to see what was going on!

 

[DragonRR]

Thats a great post by Synful Serenity and I agree 100%, from my own experience there doesn't seem a great deal of difference between the 17" 12ms Auoptronics panel and the LG-Philips 23" 16ms panel from the ghosting/blurring side.

I've been wondering about this business with some people not seeing the blurring/ghosting. There have been a number of posts claiming that some people don't see it because they have "slow" eyes. Personally I've never met anyone who doesn't see the ghosting/blurring once its been pointed out, or they can compare with a CRT. The blurring is visible if you take a photo of a screen with, for example, a scrolling RTS or Diabolo as you suggest where the background and/or characters are literally blurred when there is motion. I cannot see how anyone could not notice this because even if they have got "slow" eyes they will see the same thing even if their personal snapshot is taken less frequently, their eyes can't make clarity from a mess!

That said the latest screens are much better and the blurring is reduced to the point where you can "ignore" the issue to a large extent. I still see it if I think about it and on odd occaissions when I am looking for a unit in an RTS & miss it because it isn't properly resolved but this is very infrequent. Even with this I find myself compensating by scrolling around at a marginally slower speed than I did with my CRT!

 

[Elledan]

I've been wondering about this business with some people not seeing the blurring/ghosting. There have been a number of posts claiming that some people don't see it because they have "slow" eyes. Personally I've never met anyone who doesn't see the ghosting/blurring once its been pointed out, or they can compare with a CRT. The blurring is visible if you take a photo of a screen with, for example, a scrolling RTS or Diabolo as you suggest where the background and/or characters are literally blurred when there is motion. I cannot see how anyone could not notice this because even if they have got "slow" eyes they will see the same thing even if their personal snapshot is taken less frequently, their eyes can't make clarity from a mess!

I think that this issue has less to do with 'fast' and 'slow' eyes and more with an issue which is common outside computer displays, audio, for example.

Numerous people listen to mp3 and (worse) wma files which sound awful to me, but to them it's perfectly acceptable. A number of years ago I was one of those people.

Once I also used a 14" monitor with a refreshrate of 60 Hz. Nowadays I get this sick feeling in my stomach the moment I look at any monitor set to 60 Hz for longer than a couple of seconds.

I'm not certain how to define this phenomenon, but it's indeed interesting.

 

[Inside_line]

Does anyone know if plasmas have any of this blur effect?

 

[BillR]

Does anyone know if plasmas have any of this blur effect?

Plasma in much worse when it comes to computing. People have to keep in mind a few basics.

Film runs at 16 frames per second. Video (tape) runs at 30 frames per second. Monitors designed for TV use (plasma) don’t need to be concerned about a game at 100 frames per second; it’s a signal the designers never intended the consumer to use.

The biggest problem with anything used for TV viewing is those two different frame rates. Good TV’s come with 2-3, 3,2 and reverse 3,2 “Pull down” which is an internal computer used to compensate for what our eyes perceive.

Synful Serenity’s summery of LCD is very much right on; I have been preaching this from day one. The numbers for the most part mean nothing. I too have seen .25ms monitors that don’t blur as much as so-called .16ms monitors. It’s largely what each our mind’s eye perceives.

You can read this or any display forum until you are blue in the face, but it’s no place to make a buying decision. At some point you must go into a store and play with the units you are considering. What you see and what I see will be very different based on many different things. What ever those “things” are doesn’t matter, what YOUR eyes see is the only thing that matters. Peer pressure and cool factor should be the last reason to spend this much money.

Keep in mind, just because there are 50 Honda Civic EX’s in a line with the obligatory grapefruit launcher exhaust systems driving down the road doesn’t in itself make it a good or bad car, just a “fan boy” car. Don’t become a fan boy monitor shopper.

Go shopping and LOOK at them..

 

[johnked24]

"That said the latest screens are much better and the blurring is reduced to the point where you can "ignore" the issue to a large extent. I still see it if I think about it and on odd occaissions when I am looking for a unit in an RTS & miss it because it isn't properly resolved but this is very infrequent. Even with this I find myself compensating by scrolling around at a marginally slower speed than I did with my CRT!"


I've found that putting the scroll speed at max is better for rts, at least for me. Because the screen scrolls so fast you don't have time to see any blur, and when you stop scrolling everything is nice and crisp.