Donald Trump and Vladimir Putin both knew their first handshake would be broken down frame by frame to see who's in control ... so here goes.

The two Presidents came face-to-face Friday for the first time at the G20 summit in Hamburg, and shook before sitting down for a chit chat.

Check out Trump's play ... as they shake, he taps Putin's forearm 3 times, in rapid succession, which seems like a dominant move. Putin plays it by the book during the shake, but then points at Trump as if it's a sign of affirmation ... again, a dominant move.

It does sound stupid, but handshakes are important.