[Gordon Freechmen]

So Overlord is offering overclockable PCBs now. ( http://www.overlordcomputer.com/Overlord_Computer_Overclock_PCB_Set_p/ovrld_pcb.htm ). Now I know that a lot of people with 2B catleaps, and overclockable Overlord monitors can get their PCB to accept 120hz+. However according to the charts I have seen of the response times for these monitors they can't do 120hz.



Now the way I see it the PB2700, the Shimian QH270, and the Catleaps Q270 all use the same Panels. So in theory you could get a monitor with those response times from any of the manufacturers of Korean 2560x1440 IPS panels. So on a still grey image with these monitors you could potentially get 119hz. Though the average refresh rate of someone who is unlucky might only be 87hz. Now I was wondering as far as gaming goes. What would the actual refresh rate be? If the response time was 11ms you would get about 90hz right? So when gaming with that amount of movement would you around 90hz? And what would it look like? If you can't display 120hz but could only refresh fast enough to display 90 unique frames what would the extra frames look like? I really have no idea, and would like to know before I even though about spending 260 on a PCB.

 

[kevinsbane]

You would get 120hz operation, regardless of the response times of the pixels.

However, what would happen would be that a picture might refresh before a pixel finishes changing colours. You would not, ever, get 90fps if you were pushing a 120hz signal. You can think of it as "pixel tearing" - similar to screen tearing. Whereas in screen tearing, where the screen can't draw the picture fast enough before the next frame arrives; pixel tearing occurs when the pixel doesn't quite change fast enough until the next refresh cycle comes around. It would be much less noticeable than screen tearing, and would manifest itself is blurred colours in slow colour transitions on quick movements.

 

[Gordon Freechmen]

So then would it be better to set a monitor like this to a lower refresh rate. Say 90hz. So it has a higher refresh rate but we can avoid or at least mostly avoid pixel tearing?

 

[PCM2]

The pixel responses of IPS technology, as I've been saying for a long time are not good enough to properly support 120Hz. At least not so good that manufacturers have jumped at the idea. That's why you have to 'overclock' these panels beyond their native settings. As above, you don't get the full trailing reduction benefits of the higher refresh rate as the transitions are much slower than on snappy 120Hz TN panels. Some are in fact above the threshold of 8.33ms so you don't get 120 discrete frames, either.

What's certainly noticeable and of benefit is the increased mouse polling rates you get - everything is much smoother as you interact with the game world. I'm not really sure if that would 'feel' the same at 90Hz but anybody with one of these monitors is probably going to tell you to put it as high as you can anyway.

 

[kevinsbane]

Quote:

Originally Posted by Gordon Freechmen

So then would it be better to set a monitor like this to a lower refresh rate. Say 90hz. So it has a higher refresh rate but we can avoid or at least mostly avoid pixel tearing?

No. Pixel tearing is not as detrimental to moving to a slower refresh rate. 120 hz will still be better than 90hz.

 

[BababooeyHTJ]

I'm really tempted by these 120hz pcbs. I'm about to pull the trigger on one.
Quote:

Originally Posted by PCM2

The pixel responses of IPS technology, as I've been saying for a long time are not good enough to properly support 120Hz.

I don't know about that. There are IPS 3d tvs. At 720p they do 3d at 60fps which requires a 120hz input. I've heard good things. For crosstalk to not be a huge issue pixel response time must be decent.

 

[PCM2]

Quote:

Originally Posted by BababooeyHTJ

I don't know about that. There are IPS 3d tvs. At 720p they do 3d at 60fps which requires a 120hz input. I've heard good things. For crosstalk to not be a huge issue pixel response time must be decent.

There are no TVs with 120Hz inputs. There are TVs with 120Hz output but they don't have to produce 120 discrete frames of information (or 60 per eye in the case of some active stereoscopic technologies) and instead use frame interpolation. TVs have no need to run a 'true' 120fps or (60fps per eye) output when their input (Blu-ray 3Ds, broadcasts etc.) is limited to much lower frame rates.

 

[hollowtek]

$210. No.$75. Yes.

 

[BababooeyHTJ]

Quote:

Originally Posted by PCM2

There are no TVs with 120Hz inputs. There are TVs with 120Hz output but they don't have to produce 120 discrete frames of information (or 60 per eye in the case of some active stereoscopic technologies) and instead use frame interpolation. TVs have no need to run a 'true' 120fps or (60fps per eye) output when their input (Blu-ray 3Ds, broadcasts etc.) is limited to much lower frame rates.

Dude you can do stereoscopic 3d on many 3dtvs at 60fps in 720p. The only reason that you can't do 1080p is due to HDMI bandwith limitations. In order to do that it would be running at 120hz.. Regardless of resolution its refreshing at 120hz with good results from what I hear. Read up on gaming in stereoscopic 3d.
Quote:

Originally Posted by hollowtek

$210. No.$75. Yes.

Good for you, its not like you have any other option.

 

[PCM2]

I must apologise for not expanding my answer properly. In an effort to oversimplify something I ended up painting a confusing picture - went off course entirely. To set something straight there isn't actually a specific bandwidth limitation to HDMI preventing a Full HD signal being used at 120Hz - theoretically the 1.4a standard provides sufficient bandwidth for this. There is a port controller limitation on TVs, monitors and GPUs that means the signal can't actually be handled. Technicalities aside you are entirely correct that a 720p signal @ 120Hz can be supported by HDMI at every level of integration.

But we are talking (at least the thread poster and I when I posted the initial comment you disagreed with) about the ability to effectively support a 120Hz refresh rate in 2D. Not 3D... Stereoscopic technologies running at 120Hz essentially only need to output up to 60fps (60Hz if you prefer to split it that way) per eye. On a TV this doesn't have to be 60 discrete frames of unique information and funnily enough it isn't. But even if it were 60 unique frames being sent to each eye, the pixel response times only need to be adequate to perform at 60Hz with a 16.66ms delay between frames. Displaying a fluid picture at 120Hz for normal 2D viewing decreases the time between frames to 8.33ms and calls much more from the pixel responsiveness. These thresholds represent the absolute minimum to prevent frame overlap - it's still a case of the faster the better to a large extent.

The article I linked to in the first quote that you refuted actually explains that 120Hz refresh rates are great for facilitating stereoscopic 3D on TVs (regardless of panel type) but that doesn't equate to proper 2D capabilities or the ability to draw 120 discrete frames per second. And that doesn't mean you can run the TV at 120Hz for 2D viewing, either.

 

[Zynx87]

Quote:

Originally Posted by PCM2

The pixel responses of IPS technology, as I've been saying for a long time are not good enough to properly support 120Hz. At least not so good that manufacturers have jumped at the idea. That's why you have to 'overclock' these panels beyond their native settings. As above, you don't get the full trailing reduction benefits of the higher refresh rate as the transitions are much slower than on snappy 120Hz TN panels. Some are in fact above the threshold of 8.33ms so you don't get 120 discrete frames, either.

What's certainly noticeable and of benefit is the increased mouse polling rates you get - everything is much smoother as you interact with the game world. I'm not really sure if that would 'feel' the same at 90Hz but anybody with one of these monitors is probably going to tell you to put it as high as you can anyway.

Great article, and I hope I came away with the correct assumption that you want your pixel response times lower than frame transition times, which in the case of 120Hz would be 8.33ms. It would be nice to see what the results of one of these overclockable Korean or Overlord monitors would look like in that test.

 

[PCM2]

That is exactly it. It would be interesting to see that, yes. They don't have particularly aggressive pixel overdrive and shouldn't really exhibit different pixel behaviour to other similar examples in the OP's table.

 

[kevinsbane]

Quote:

Originally Posted by PCM2

That is exactly it. It would be interesting to see that, yes. They don't have particularly aggressive pixel overdrive and shouldn't really exhibit different pixel behaviour to other similar examples in the OP's table.

Having read your article, I must disagree with certain aspects.
Quote:

t 120Hz the transition time between frames is lowered to 8.33ms (1/120= 0.0083s= 8.33ms) which can increase the apparent fluidity of the image if certain other conditions are met.

It increases the apparent fluidity of the image regardless of the other conditions. 120hz operation on a 2B Catleap does little, however, to counter motion blur and ghosting. Fluidity is up, ghosting is mostly the same.
Quote:

For optimal visual performance at a 120Hz refresh rate the monitor would have to complete most pixel transitions within 8.33ms to prevent 'frame overlap' - with even lower values being preferable.

This is very true, and absolutely essential for 3D operation. And for optimal performance, this is true in 2D too. However, in practice, I have not noticed a serious degradation in visual performance on my 2B, even given the relatively slow transition times. Frame overlap is, in my opinion, not an issue - we already suffer from this problem! It's called ghosting.
Quote:

Even the newest IPS and PLS (Plane to Line Switching - Samsung's version of the technology) models struggle to keep responses consistently below the 8.33ms threshold, which is the bare minimum for 120Hz to work effectively

I would say rather that IPS/PLS struggle to keep response times below 8.33ms - the bare minimum of optimal 120hz operation.

Consider this thought experiment. A white line on a black background is moving across the screen at a constant speed. It moves at a speed of 1200 pixels a second. At 60hz, your line moves across the screen in increments of 20 pixels per frame - every frame, the white line will move to the right 20 pixels, be lit for 16.7ms, then go dark as the line keeps moving right. It takes 11ms (approximate) for the line to change brightness from black to white. The ghosting persists for approximately 11ms after the fact. There will be the afterimage of 1 line for 11ms.

Let's crank up the refresh rate, yet, maintain the speed of the line. It moves at 1200 pixels a second - but there are twice the frames. Your line now moves at 10 pixels every frame - there's a new "inbetween" frame. The line moves right 10 pixels; it tries to turn to white, but doesn't quite make it there. Then it changes back to black. The response time is still 11 ms - so the image ghosts for up to 11ms (the same as at 60hz operation). But because there are twice as many frames - the movement of the line across the monitor will be twice as smooth. There may be slight artifacts with regards to colour - but in my experience... I haven't seen those artifacts when running PixPerAn at 115hz; and believe me, I was looking by using PixPerAn's pixel transition tests.

It's not something I would sell to the general public as "120hz monitors". They aren't 120hz monitors. They don't work exactly like 120hz monitors ought to work. But you can probably get 80% (WAG) of the benefit of a true 120hz monitor by running a 2B Catleap at 120hz. And you get the benefit of IPS viewing angle technology, 1440p resolution and more stable colours compared to TN.

 

[PCM2]

I do feel that some aspects of the article come across as a bit negative and dismissive towards the technology. When I wrote it initially it was designed to make people appreciate some of the reasons why manufacturers aren't adopting 120Hz IPS/PLS technology and why it isn't directly comparable to 120Hz TN tech. If I were to write it today I reckon it would take a slightly different tone. I might rebalance it a bit some time when I get the chance. It isn't really all that visible on the site any more and I kind of swept it under the rug a bit.

A more recent reflection of things can be found here - http://pcmonitors.info/forum/topic/korean-2560x1440-ips-imports#post-20900.

There are a few points in the article that really agree with what you are saying (and article aside - there are absolutely benefits to be had from 120Hz IPS).
Quote:

You might argue that even with the reduced benefit compared to their TN panel counterparts the 120Hz refresh rate is still worth it as it improves the 'connected feeling' compared to running the same monitor at 60Hz. Unfortunately the manufacturers seem to feel that they aren't quite where they want to be to take their IPS and PLS to the next level. And to some extent consumer expectation doesn't quite line up with what is achievable from the current technology.

This is essentially stressing that there is some benefit in fluidity but that manufacturers aren't happy to pump out this technology just at the moment. It isn't really a direct justification for that - it isn't optimal by any means but there is benefit to it, no doubt. The article really concludes with an unfortunate assessment of where LG are currently focussing their efforts (and it isn't 120Hz in any shape or form), though, and that perhaps PLS is a more likely candidate for this sort of thing.

And in relation to a proper/official 120Hz display of this variety:
Quote:

It might well be aimed primarily at enabling stereoscopic 3D viewing but there would be some secondary benefits such as a reduction in visible trailing and superior 2D responsiveness.

I'm also working on a much more thorough article assessing the factors affecting the responsiveness of a monitor. This will look at, amongst other things, why refresh rate alone can be so influential to a monitors response performance irrespective, to some degree, of pixel responsiveness.

 

[BababooeyHTJ]

Quote:

Originally Posted by PCM2

But we are talking (at least the thread poster and I when I posted the initial comment you disagreed with) about the ability to effectively support a 120Hz refresh rate in 2D. Not 3D... Stereoscopic technologies running at 120Hz essentially only need to output up to 60fps per eye.

Thats right 60fps per eye, every second. Thats 120 frames every second. Thats how tri-def works.
Quote:

On a TV this doesn't have to be 60 discrete frames of unique information and funnily enough it isn't.

Have you ever gamed in 3d? I'm talking about gaming in 3d, not movies. Do you understand how active stereoscopic 3d content is displayed on a monitor? Its two completely different images per eye. Crosstalk (ghosting) is a term used when the image for one eye bleeds into the image for the other eye. For crosstalk to not be an issue pixel response time must not be that bad.

 

[PCM2]

You're completely straying off topic here and employing a pointless patronising tone that is doing you no favours at all. As I was trying to tell you, what you are saying has no bearing whatsoever on the original post or on how suitable IPS technology is for true fluid 120Hz playback. Just take 3D out of the equation as that isn't what the point of this thread was until you decided to push things down the wrong path. My original point was simply that IPS technology, in no official capacity (TV or otherwise), currently supports true 120Hz input and output. 60Hz in each eye does not require the same level of pixel responsiveness as 120Hz. Try connecting a TV to a PC and running it in 120Hz. You can't - it's not possible, regardless of resolution.

 

[BababooeyHTJ]

You completely missed my point.
Quote:

Originally Posted by PCM2

60Hz in each eye does not require the same level of pixel responsiveness as 120Hz.

That doesn't even make sense. If anything its more important.

 

[PCM2]

I've been very busy today and my mind has been elsewhere so perhaps I'm not making myself clear. Perhaps I'll wake up tomorrow and realise I have been talking complete rubbish. If not I'll let somebody else explain it to you perhaps.

 

[Makav3li]

Quote:

Originally Posted by BababooeyHTJ

You completely missed my point.
That doesn't even make sense. If anything its more important.

You're wrong Bababooey, just drop it.

 

[BababooeyHTJ]

You haven't explained your point at all. You're acting as if stereoscopic 3d doesn't require a separate image for each eye. It does and if the pixels don't refresh fast enough you'll see an after image. Have you ever gamed in 3d?

My point that you seem to have missed is that if a 3d tv can pull this off then the pixel response times must be better than some people give it credit for and will benefit from the higher refresh rate.
Quote:

Originally Posted by Makav3li

You're wrong Bababooey, just drop it.

How so? You seem to know better. Explain how.

Either way, I'm dropping this and adding the both of you to my ignore list.