"Quickstep. I asked a simple qustion which you don't seem to have read properly. No vidio images can give the exact time the body weight is over the left foot"second step" Is it at the beggining or end of the of beat three? Dave"
Actually, if you look at videos you will often find that you can narrow this down quite a bit. For example, on Jonathan's feather (which I don't completely agree with, but it's something we can all look at) there's really only maybe three frames when both of his feet are stationary on the floor. That's a tenth of a second. At 30mpm, a beat is a half second. So, if you figure out how to match things back up to the music, you could know within a 1/5 of a beat.
I think that you will find that it is rare to position a foot fully but not immediately weight it. I won't say it never happens, only that it is not the usual action. Usually, your foot will keep moving pretty much up until the point where you have to put weight on it (or fall flat on your face).