Kill ambient light with flash

Here's a simple example of how to kill ambient light (perhaps from a distracting background) and light the subject with off-camera flash, triggered optically.

First, our control test - meet "Ted" (given to me by my Grandmother, nigh on 50 years ago):
Above, we have Ted, sat on a smoked glass coffee table with a white material background. The camera is set to auto (green box) - the popup flash created the shadows.

Here's Ted again, but this time with the camera in Aperture Priority mode with no flash.

Personally, I do not rate either photo, especially the background, so lets get rid of it...

The camera is set to Manual, a suitable aperture selected and a shutter speed that results in a plain black background. Ted is still there, so is the white background, even the ambient light has not changed - it's just that the camera settings did not absorb any light, so we need to add some.

Next, we set an off-camera flash gun to "slave" and set it down to the left. We choose a medium power setting, set the flash meter to match the cameras settings and ask Ted to hold it for a moment whilst we take another shot. Our hand sheilds the popup flash from illuminating Ted.

Using the result on the flash meter, we adjust the flash and take the above shot - much better.

Finally, we add a silver reflector to the right to fill in some of the shadows and we're done.

All photos are straight out of the camera (no post processing)
Canon 7D with the popup flash triggering a Yongnou YN568EX flash in slave mode.