the 70 000:1 ration is an active contrast ratio on your monitor . it's done by technology to increase the effect and gives better image quality in dark image in game . most monitor are 800:1 1000:1 2000:1 contrast native not active .
Active contrast ratio is a BS
Vsync stop images from getting on each others to avoid tearing and lock FPS to your maximum monitor output ( a display can be forced to do more but it will damage it in the long run )
edit : The human eye isn't fonctioning by FPS it is a streaming of information ( like every other eye in the animals world .
your eyes sees every frame something can output . so it could not be possible to differences 60fps from 7 000fps from your perspective but your brain sees all the images . so in fact it buys you ms of reaction time between 60 fps and say 200 fps.Edited by Marc-Olivier Beaudoin - 1/28/11 at 11:00am