These shots are most certainly flash. The dark ambient background is achieved by stopping down the shutter. Shutter controls ambient, aperture controls flash ex

These shots are most certainly flash. The dark ambient background is achieved by stopping down the shutter. Shutter controls ambient, aperture controls flash exposure. Assuming of course you're not setting it faster than your cameras sync speed (which now can be alleviated by high speed sync) on high end cameras. So now you have a well exposed subject, with nearly dark background.