The human visual system does not see in terms of frames; it works with a continuous flow of light information.[citation needed] A related question is, “how many frames per second are needed for an observer to not see artifacts?” However, this question also does not have a single straight-forward answer. If the image switches between black and white each frame, the image appears to flicker at frame rates slower than 30 FPS. In other words, the flicker-fusion point, where the eyes see gray instead of flickering tends to be around 60 Hz. However, fast moving objects may require higher frame rates to avoid judder (non-smooth motion) artifacts—and the retinal fusion point can vary in different people, as in different lighting conditions. The flicker-fusion point can only be applied to digital images of absolute values, such as black and white. Where as a more analogous representation can run at lower frame rates, and still be perceived by a viewer. For example, motion blurring in digital games allows the frame rate to be lowered, while the human perception of motion remains unaffected. This would be the equivalent of introducing shades of gray into the black–white flicker.
QUOTE FROM WIKIPEDIA
. It's pretty obvious if you come back from playing a certain v-synced game.
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