>I (and many, many others) notice lag in games with v-sync turned on vs off, and we're talking about single digit milliseconds there.
Indeed, I found this recently out in a double-blind kind of way, when running at 165hz. I had to take out my GPU to fix the fan, so I wanted to try playing some demanding games on my integrated Intel GPU. I switched settings to the lowest (along with the game itself auto downgrading settings). After I put my GPU back, I put all the settings back, or so I thought. I was feeling some input lag and the mouse a little "floaty" but thought I just imagining it for a day or two. Afterwards I checked settings and lo behold, VSync was on.
I was surprised that I could tell the difference when running at 165hz and 165 fps.
I feel like there must be something way wrong with the way vsync is implemented in most games. It often feels like it adds massive latency (like an entire extra buffered frame, like bad implementations of triple buffering), but if my FPS is close to what it would be with vsync, then I don't see why it should add much latency.
That is to say, on my 60Hz monitor, I don't feel much difference between 60 FPS and anything above with vsync off. But if I go from from 70FPS (vsync off) to 60 FPS (vsync on), it's yarrgh unplayable, as far as first person shooters go.
With vsync, a late frame delays input by a whole refresh cycle. When your hardware is only capable of average frame rate similar to your refresh rate, there will be plenty of those.
What is your screen refresh rate? With Vsync on, you are capped to the screen refresh values. If you have a 144Hz screen and you're running 165FPS with VSync off, you will run 144FPS with VSync on. But if your GPU struggles to hit 144FPS, with Vsync on it will drop instantly to 72 FPS, then to 36 FPS (assuming no GSync/FreeSync).
Indeed, I found this recently out in a double-blind kind of way, when running at 165hz. I had to take out my GPU to fix the fan, so I wanted to try playing some demanding games on my integrated Intel GPU. I switched settings to the lowest (along with the game itself auto downgrading settings). After I put my GPU back, I put all the settings back, or so I thought. I was feeling some input lag and the mouse a little "floaty" but thought I just imagining it for a day or two. Afterwards I checked settings and lo behold, VSync was on.
I was surprised that I could tell the difference when running at 165hz and 165 fps.