Need help understanding Refresh rate (Hz) and Response time (ms) relatonship

[Pete_the_Puma]

Hi all,

I've been reading quite a lot about monitors recently and am very interested in eventually upgrading my current 2560x1440 @ 60Hz display to a 2560x1440 @ 120 Hz display (One of the Korean monitors that can be Oc'd to 120Hz, no 1440 is 120Hz out of the box, even the 1000$ Dells and Asus's)

My question is the following. How does response time factor in with refresh rate. What I mean is this:

At 120Hz (and assuming 120 FPS output from GPU) you are getting
120 frames per 1 second =
120 frames per 1000 ms =
1 frame every 8.3ms

So how is having any refresh speed higher than 8ms beneficial at all if the next frame is not coming before 8.3 seconds anyway?

This is even worse at 60Hz where you get one frame every 16.6 seconds. So how is a 2ms refresh speed 60Hz monitor any better than a 10ms 60Hz refresh monitor? The next frame is not getting there before 16.6 ms anyway.

I must have missed something. Will be researching this online but maybe someone here knows the answer. This is a good website but I haven't found the answer there yet...

http://www.blurbusters.com/

Thanks in advance,

P

 

[geofelt]

Good question.
And... is your graphics card good enough to deliver 120fps or even 60fps anyway?

I think there is more to it though. I will follow this thread.

 

[Pete_the_Puma]

Edited the post. I am assuming a perfect 120 FPS output from the GPU to simplify this.

Also posted on another forum here:

http://120hz.net/showthread.php?3357-Please-explain-relationship-of-Refresh-rate-%28Hz%29-and-refresh-speed%28ms%29

Also sent a PM to someone who know everything about monitors, will keep you updated. I'm sure it's something simple I overlooked.

P

 

[Pete_the_Puma]

Wow I got some great answers on the 120Hz.net forums, I will post a short version of the explanations here for those interested, very cool concepts about monitors for people to understand.

So assuming a 120Hz monitor and a 120 FPS output from the GPU, every 8.3333 ms (1/120th of a second) a new frame is generated and sent to the monitor to display. The pixels START changing colors. The response time is the time it takes for the pixels to go from the old frame color to the new frame color. The shorter the better obviously. In a 120Hz monitor if the response time is for example 1ms (for all pixels, see below) it will take 1ms for all pixels to change and then for the remainder of this cycle (7.333 next ms) the frame will be static. We can all see how if the response time is greater than 8.333 ms for a 120Hz screen this would be terrible as the pixels would never quite achieve the final color of the current frame before having to start displaying the next frame again.

Of note response time is not uniform! The reported response time is actually a weighted average. For any given monitor the response time varies for pixels depending on the colors they are going to/from, more specifically the shade of grey of the old/new frame.

Also mentioned in that thread is the fact that most monitors with response times of 1-4ms use something called "overdrive" which will change the pixels color faster but will sometimes overshoot leading to a different kind of image distortion (not blurriness as it is fast, but sometimes does not get the exact color wanted).

Again I take no credit for these concepts, just regurgitationg what I learned from:

http://120hz.net/showthread.php?3357-Please-explain-relationship-of-Refresh-rate-%28Hz%29-and-refresh-speed%28ms%29&p=26900#post26900

Hope this educates some of you guys too

P