Method Two / Balance light with shutter speed
1 Expose for ambient light
Like the first method, set Manual mode and expose for your scene with just ambient light and attain a balanced exposure. Once again, this resulted in an aperture at f/5, shutter speed at 1/250 sec, and ISO100.
2 Underexpose the scene
Underexpose the ambient light by increasing the shutter speed by one full stop – in this case, we changed our shutter speed from 1/250 sec to a faster 1/500 sec, darkening the entire image.
3 Add your flash
Set Auto FP mode on your flash and adjust the power until you have a good exposure on your subject. Ensure the light doesn’t spill onto the background and that your subject isn’t overexposed by the flash.