What is VSync? & LCD Monitor Refresh Rates

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The Confusion about VSync

Turn off VSync to increase game performance. You’ve probably heard it, and, depending on how you define performance, it’s accurate. If gaming performance to you is based only on frame rates, then yes, VSync indeed limits frame rates. If you care about how those frames look, then VSync can be good in many cases.

The Myth within the Myth

A lot of the VSync confusion likely stems from the myth that LCD monitors don’t need refresh rates. While it’s true that an LCD monitor could theoretically leave unchanged pixels alone and only change the ones that need it, that’s not how video signals, be they computer or media based, work.

Computer graphics work by rendering frames, and film and television are based around filming frames as well. Before you lament the lazy engineers who haven’t completely junked technologies evolved to incredible sophistication over a century to take advantage of decade old LCD technology, how much trouble is the FCC having getting people off analog rabbit ears?

Though flat-panel TVs are taking over, the overwhelming majority of North America, let alone the world’s, televisions are still cathode ray tubes. But computer monitors, at least on a gaming PC, are LCD, so why can’t computer graphics, if not media based video, take advantage of this? After all, computer graphics have only been evolving for three decades or so, and LCDs have been common for the last third of that period.

It’s still a massive undertaking: using fields (parts of the screen in motion) instead of frames is being kicked around, as it has since the first LCD monitors were thought of, but that is a huge change in how graphics are handled.

Finally, where are the benefits? An MMO, FPS, or RTS player’s perspective is constantly moving, so the entire frame is constantly changing. You can argue that it would help in flight or driving games, where the cockpit doesn’t change much, but that ignores the lighting and shadow effects.

That leaves adventure, platform, and puzzle games with constant backgrounds throughout a scene or level. These games are far less graphically demanding than those mentioned above specifically because of the fixed perspective, so they don’t drive graphics technology. Those that do turn up the eye candy use tricks like having your avatar carry a light source, the point of which is moving lighting and shadows. Those obviously affect most of, if not the whole screen.

What Does this Have to do With VSync?

Well, I’ve come across forum posts that say there is no such thing as a refresh rate on an LCD monitor, so always keep VSync off. First I want to dispel that, and then I want to to provide some information to help us figure out what VSync actually does. In simple terms, it ties your computer’s frame rate to your monitor’s refresh rate.

While a frame rate above sixty is best for gaming, a frame rate that is much higher than your monitor’s refresh rate can cause “Tearing.” Since most LCD monitors have a 60Hz refresh rate, that’s not a lot of room for error.

“Tearing” is the name given to the picture on your screen looking like it was cut into horizontal strips, and incorrectly lined up when put back together. Vertical objects and textures, like a pole or a picket fence, look particularly odd.

What’s happening is that every time your monitor puts up a frame, it’s actually putting up the current frame and a fraction of the next one, broken up horizontally. The amount your perspective has moved horizontally between the frames increases the amount by which it looks like your screen has torn.

VSync can solve this by capping your GPU’s frame rate with your monitor’s refresh rate, making things look a whole lot better, as long as your uncapped frame rate is higher than your monitor’s refresh rate.

This post is part of the series: VSync: On or Off? – Yes; Set It on a Per Game Basis

VSync can be good or bad, depending on your monitor’s refresh rate, the game you’re playing, and how fast your computer can run it. Luckily, it’s easy to set it up to run automatically when playing games where it helps.

  1. Terrible Performance Tips – Keep VSync Off
  2. So Turn VSync On or Off?
  3. Setup VSync and Triple Buffering for No Tearing and Best Frame Rate
  4. Turning On VSync and Triple Buffering If Your Game Tears