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++++ALERT: You are reading an out-of-date version of the guide and wasting your time. Read the PDF for the most accurate up-to-date info.It's best to download the PDF and use a proper PDF reader. Google's formatting of PDFs breaks all of the links. Link to directly download the PDF. I have stopped updating the text in the thread because the forum's limited code makes it far too time-consuming to change images and add text.++++
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Monitors and Frames Per Second

Yes, we’re starting with a part that isn’t even included in our budgets. But without this information, we cannot create an informed build. That’s because your monitor’s resolution will dictate your video card needs, and the video card commands a large portion of the budget, as it should.

This section is not about actually selecting a monitor, however. Here, we will focus on only two factors that will directly influence your overall gaming experience: Resolution and Refresh Rate. You probably already know what resolution is, so let’s save resolution options for later and take a moment to discuss refresh rate. In that respect, monitors generally come in two flavors: 60 Hz and 120 Hz. Some people mistakenly view this as a direct indication of frames per second (FPS). While this does have a significant and somewhat absolute correlation with frame rate, it’s important to understand that FPS (number of frames per second being processed) is independent of the monitor refresh rate, which is, you guessed it, the rate at which the monitor’s hardware is refreshing the display. Why does that matter? Answer: Just because you have a 60 Hz monitor doesn’t mean that anything beyond 60 FPS is useless and unnoticeable. You can notice a benefit with a frame rate higher than 60 FPS, even on a 60 Hz monitor.

Over the years, people have parroted some variation of the phrase: “The human eye can only perceive 30 frames per second.”—or 40 or 60 or 15 or 100. There are too many variations in the way digital media is presented to make such a blanket statement. To learn more, read this article: LINK

Forget anything you’ve heard about how many frames per second the human eye can see. We aren’t watching a movie. We’re playing a game that requires your physical interaction as well as dynamic input from other hardware (i.e., mouse and keyboard). It’s a different experience, and here’s why.

When you play a game, you have the option to enable or disable vertical sync (VSync). When you enable it, your video card’s goal will be to keep the frame rate of the rendering engine (the game) equal to your monitor’s refresh rate. In this case, 60. Assuming you have a video card powerful enough to achieve this, VSync turns your monitor into the frame rate bottleneck. This isn’t a bad thing, visually. 60 full frames per second is the maximum your 60 Hz monitor is capable of allowing your eyes to see. It’s the frame rate you want to achieve, minimum, in most cases.

When you disable VSync, your video card will work independently to output the highest frame rate it’s capable of producing under that game engine at the graphics settings you’ve chosen. So, without VSync, you might run a FPS monitoring program and see that you’re getting 90 FPS on your 60 Hz monitor. What you’re actually seeing is the FPS that the GPU can produce before it reaches your monitor. The monitor is processing all of those frames, but it is not displaying every whole frame. But this surplus of frames, so to speak, lends itself to another absolute necessity in fast-reflex games such as First-Person Shooters, especially online: low-latency mouse response. Mouse lag.

In the simplest of terms, when in VSync mode, your video card waits for the monitor's next refresh operation before rendering the next frame. In such a case, when you move your mouse, it must wait for the game engine to respond, which is waiting for the video card, which is waiting for the monitor to refresh, and then you see your cursor/crosshairs move. Because the video card is depending on the monitor, it has to wait for the next refresh cycle before rendering the next frame. If the frame rate is even lower than the refresh rate, the monitor is now performing more refresh cycles before the next frame is rendered, causing an even longer waiting time for the mouse to respond.

The latency between the video card and the monitor is the largest, which is why watching a cut-scene at 24–30 FPS doesn't look bad to your eyes, but trying to manipulate your character in real-time at that frame rate can feel loose, slow, and unresponsive. Ideally, you want to be able to render more than 60 FPS consistently, without VSync, so that your video card is always ready for your monitor to show a frame before the next refresh cycle.

Here’s a visual example, involving two theoretical players with the same hardware and precisely the same skill level:

The above chart only depicts a stop/aim/shoot scenario, which doesn’t even take into account the lateral movement of the players or even the crippled accuracy that results from Player B’s lower frame rate, but as you can see, the additional time spent waiting for frames and refresh cycles nearly doubles the total latency between the player’s mouse movements and the action on the screen. If you pit these two players against each other, you’d certainly want to be Player A. You would see your own movements before Player B does. You’d even see your opponent’s movements before he does because the game engine’s response is not dependent on the monitor (therefore the enemy is in the player’s virtual line of sight at the same point in time in both scenarios).

I added human reaction time to the graph to show that the input-to-display time all occurs in a fraction of the time it would take even a skilled player to react and compensate. This lag between your mouse and the monitor's display of your movements is only a matter of milliseconds, but it is noticeable when you have to make frequent, split-second movement decisions in a game.

Test your own reaction time at humanbenchmark.com

But like most benefits, there’s a cost. With extra frames comes the potential for screen tearing, which is when the screen appears torn between multiple frames. Some people hate it, and some people don’t notice it. Here’s an extreme example of screen tearing:

Image borrowed from tweakguides.com

Notice the different horizontal sections of the screen that are out of vertical alignment. As I said, this is an extreme example to show its effects clearly. Tearing most commonly occurs at frame rates higher than your monitor’s refresh rate because the monitor is trying to display more frames per refresh cycle. This will cause the monitor to display the next frame before it's finished displaying the previous frame. It’s more noticeable in some games, and completely unnoticeable in others.

This post was edited on 3/20/14 at 3:32 pm