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I’ve been searching the Internet for advice on my next PC/console monitor purchase and came across a good deal on the LG D2342P-PN. It’s an LED monitor with all three connectors I want, and even 3D mode at 120Hz—which I didn’t want but why not have?

Then, I read some reviews of it and the biggest simple complaint I read was that this monitor does not support 120Hz in 2D mode. Huh? Who needs 2D mode at 120Hz? The last time I checked, 60fps was the speed everyone wanted their games to run in, which is the same as the refresh speed of most monitors, but now we’re aiming for, presumably, 120fps? Or, is it 60fps in 120Hz, that we want? (Even then, why?)

What are the advantages of running a monitor in 120Hz in 2D mode (for general use, films and games)?

I understand why 120fps in 3D is good (single eye flickering, or whatever it’s called, which in effect produces 60fps across both eyes), but why in 2D mode?

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  • hz, ms , fps .. all mind boggling terms. Can you see it. Then it works. Do you need 120hz?Not sure.. then who cares.
    – Piotr Kula
    Jan 5, 2012 at 15:24
  • 120 Hz is faster than 60 Hz, so it has to be better. Oh wait, we can't tell the difference above 60 Hz... What do you know! Another case of manufacturer-initiated number inflation to make us all waste our money! Another interesting fact: most movies you watch are only shot in 25-30 FPS (since that is more cinematic)!
    – Breakthrough
    Jan 11, 2012 at 13:17

5 Answers 5

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There are two main benefits of using a 3D display in 2D:

  1. It is possible, if your GPU is capable, to run games at up to 120 FPS for improved smoothness. A 60Hz display would either be capped at 60 FPS (with vsync on), or would result in "tearing" (with vsync off). So a 120Hz display lets you make use of any extra frames (above 60 FPS) that can be rendered by the GPU.
  2. To improve the smoothness of general computer use:

The [3D display] was my first exposure to 120Hz refresh displays that aren’t CRTs, and the difference is about as subtle as a dump truck driving through your living room. I spent the first half hour seriously just dragging windows back and forth across the desktop - from a 120Hz display to a 60Hz, stunned at how smooth and different 120Hz was. Yeah, it’s that different.

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  • Cheers for the info and link. Interesting article.
    – TomaszRykala
    Jan 5, 2012 at 19:52
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It always depends upon the software and features, but one potential difference is when vertical sync (vsync) is enabled. This is often enabled to eliminate the possibility of partially rendered frames from showing up on the screen. If it is enabled, the software must wait for the blank state/vsync/magic between displayed frames on the monitor to make the swap. This means that if software can only render 58 fps (60hz monitor), then it misses a sync and must wait for the next one. In practice, this effectively reduces your fps to half the Hz so your effective fps is 30 instead of 58 on a 60hz monitor. 120 hz refresh would reduce the time needed to wait. You still wind up with fractional reduction in fps, but it would be different. In addition, there is input lag inherent in vsync, and I have seen it stated that 120hz vsync has less than 60hz.

Note that most people, including myself, disable vsync when possible anyhow, and many games are locked to a "60fps/tics/magic" physics simulation etc..

All of this is going to be minor, so listen to your wallet.

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The frames per second of the game is different to the refresh rate of the monitor.

Higher refresh rates on the monitor give you a more stable picture - regardless of whether that picture is being changed by the computer at 60 frames per second or 1. When monitors were cathode ray tubes it was definitely the case that you could see flickering at 60Hz or even higher refresh rates so a 120Hz monitor would effectively be "flicker free". With LCD and LED displays this is less of an issue, but going to 120Hz could be beneficial, but it's unlikely.

However, it's more likely that it's because the monitor is operating in 120Hz anyway regardless of the 2D/3D mode.

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  • When monitors were cathode ray tubes it was definitely the case that you could see flickering at 60Hz or even higher refresh rates so a 120Hz monitor would effectively be "flicker free". Especially when there were CRTs on-screen while filming. :-D
    – Synetech
    Dec 26, 2012 at 19:43
  • CRT flickering is not a simple matter of refresh rate. CRT monitor have phosphor coating that glows after being hit by a beam and then some time after. So the flickering comes when refresh rate is slower than phosphor afterglow. You can have flicker-free CRT at 20Hz, it just won't look good with fast-paced action. My old monitor showed no flicker, but when I swapped it for more expensive one, it looked like a stroboscope. Same refresh rate, just different tubes.
    – Agent_L
    Aug 26, 2014 at 9:02
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Hz and Fps are totally different things

Hz is hardware refresh rate of the monitor. So it means in every hertz, every liquid crystals are refreshed on display.

Fps (frame per second) means graphics cards image output speed.

On complicated image produce, count of fps will drops according to your graphic cards power. But display devices displays images in constant hz

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  • 3
    I know what these abbreviations mean, but my question is - is there a real benefit for the end user, in running a monitor in 120Hz, with a game say in 60fps. Or a difference between 60fps and 120fps (visible). Because personally, I can't think of any.
    – TomaszRykala
    Jan 5, 2012 at 15:06
  • Or in another way - what's the visible difference between a monitor displaing a 2D game in 60Hz vs 120Hz.
    – TomaszRykala
    Jan 5, 2012 at 15:07
  • More sharpen images =) If your brain can feel the difference ;) Basically It's up to human brain functions.
    – Sencer H.
    Jan 5, 2012 at 15:15
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    Most people can tell the difference, I've found. It may not be worth the cost to you, but you can tell. I'd encourage you to try and see one in person.
    – Shinrai
    Jan 5, 2012 at 15:21
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    Whether you can tell the difference, depends on a lot of factors. A person's eyesight actually has little to do with it. Flash a single bright frame at 120 Hz, and everyone will see. You'll even be able to recognize objects drawn on it. Then again, drop a single black frame in an animation playing at 120 Hz, and no one will even notice something was missing. It's a common misconception people can't see over 25 Hz.
    – Marcks Thomas
    Jun 22, 2012 at 19:35
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What everyone is ignoring here is your health. You may not notice any frame rate above 60 hz but your eyes do. In between each frame on an LCD/LED, the screen goes dark before the next frame is shown. This is also true in film projection. You don't notice it because your brain somehow hides this fact. However, your eyes have to compensate for that instant of darkness by widening the pupil. When the next frame is shown the eye has to close the pupil down again. Your eyes can do this faster than 60hz.

This is why your eyes can feel tired or sore after hours on the monitor or in a theater. You vision can be blurry and over time this can diminish your eyesight. For the sake of your eyes get the highest speed monitor you can. Even 480hz isn't too much.

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  • Oddly enough, nobody (still) has mentioned the key term in regards to refresh-rate: eye-strain.
    – Synetech
    Dec 26, 2012 at 19:45
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    Seems highly implausible. The inability to notice darkness in between frames is not a trick of the mind, our eyes are actually incapable of registering it at sufficiently high framerates due to the rods having a non-instantaneous response to light intensity. Also, a lot of artificial lighting flickers at twice the mains frequency, typically around 100 Hz. Moreover, nerve cells 'wait' a few milliseconds before accepting the next signal to avoid reflections. This mechanic suggests pupils contract and expand at no more than 70 Hz. I'm no biologist, but would appreciate sources for this answer.
    – Marcks Thomas
    Dec 26, 2012 at 20:32

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