Method one / Balance light with aperture
1 Expose for ambient light
Set Manual mode and expose for your scene with just ambient light until you attain a balanced exposure. We settled on our aperture at f/5, a shutter speed of 1/250 sec (our camera’s max sync speed), and ISO100.
2 Underexpose the scene
Next, underexpose your scene by about one stop by narrowing the aperture. For us that meant changing it to f/7.1. No other settings should change; shutter speed and ISO remain the same at 1/250 sec and ISO100.
3 Add your flash
With the flash camera-left aiming at the subject, set the flash to Manual and increase the flashgun power until it exposes the subject perfectly. Make sure the light doesn’t spill onto the background.