Some slow-mo video examples
I wasn't sure I could capture the benefits of G-Sync with my cheap slow-motion video camera, but it wasn't terribly hard to come up with a meaningful example. All I had to do was find a scenario where the differences between vsync, no vsync, and G-Sync were apparent to the naked eye.
In this particular case, I wanted to compare the benefits of G-Sync to regular vsync on our fast 144Hz display. The scenario I came up with is in Skyrim, at 1080p resolution, on a GeForce GTX 660 graphics card. Frame rates fluctuate from about 60 to 85 FPS, and in this case, the camera pans around my character in a 360° arc, creating the sort of motion where both tearing and vsync quantization are easily spotted.
I recorded the results at 240 FPS, substantially faster than the display can refresh itself. Please pardon the low resolution and especially the different exposure levels. The camera auto-adjusted to make the scene look darker at lower refresh rates, and there wasn't anything I could do to remedy that. That said, I still think these little videos, which came out of the camera unretouched and went straight onto YouTube, do a decent enough job of illustrating the relative smoothness and motion-related artifacts of the various display modes. Let me walk you through them.
At 60Hz without vsync, you can see how motion steps forward with each display refresh in very noticeable increments. Also, tearing is readily apparent. Oftentimes, multiple "seams" between rendered frames are onscreen at once. The tearing becomes easiest to notice starting at about 20 seconds into the video, as the city walls and the cathedral lurch by unevenly.
In this case, since frame rendering rates are generally above 60 FPS, switching on vsync looks like a clear win. The tearing artifacts are gone, and the animation advances fairly evenly. However, objects near or far from the camera, in the foreground and background, still advance in relatively large steps from one frame to the next.
Ah, see? At more than twice the refresh rate of the previous example, the animation looks much more fluid. However, without vsync, tearing is still prominent. The worst of it begins at about 16 seconds into the video, as the advancing hillside and walls appear to "waggle" from top to bottom as new and old frames intermix onscreen. Kinda ugly.
Here's the near-perfect experience offered by G-Sync. The tearing is gone, the waggle is banished, and the animation is vastly more fluid. At full speed, the result is glassy smooth perceived motion. Compare this video to the one at 60Hz without vsync, which is how most hard-core gamers tend to play, and the contrast is stark. Good grief. What have we been doing all these years?
Once you've seen the G-Sync video, you can appreciate how even this mode, with vsync enabled at 144Hz, isn't ideal. Watch as the cathedral swings by in the background with the halting, uneven motion caused by vsync quantization. Almost looks as if the frame update intervals are short-short-long, short-short-long, and so on. The animation looks a darn sight better than vsync at 60Hz, but even at 144Hz, G-Sync's output is simply more correct and desirable.