Bouncing Speedlight OutputIt’s important to remember one lighting rule when using fill-flash: the larger the light source relative to your subject, the softer your light will be. By using a diffusion dome on my speedlight, I do spread out the light, but this is still a small light source, so the fill won’t be as soft as if I had used a larger light.
If I want less shadows and a softer fill light, I have to make my source larger. To soften my speedlight, I use bounce flash. Bounce flash is created by bouncing your flash off a surface and back onto your subject. Since the bounce surface generally is a lot bigger than the flash, the light will be softer. White ceilings are great bounce surfaces. Just rotate your flash head at an angle to project up to the ceiling and back down to the subject. Since the flash output is still being measured TTL, you should get good exposures. If you need more or less light, adjust your flash output.
Outside, I bounce flash off a reflector. A three-foot-diameter reflector will soften TTL flash dramatically, providing a nice, silky fill light. A great trick to add warm fill light to a portrait is bouncing your flash off a soft gold reflector back onto your subject. The portrait will look like it’s illuminated by warm evening sunlight.
I use both on-camera and off-camera speedlight shooting for fill-flash. If I’m shooting in a busy area with lots of people, I’ll shoot on-camera fill-flash with my diffusion dome attached. If I have more time and less crowded situations, I prefer to trigger my flash off-camera using a Nikon SU-800 Wireless Speedlight Commander or the RadioPopper system. Off-camera flash allows much more flexibility in aiming the flash to fill in shadows.
High-Speed-Sync Fill-FlashI photograph a lot of fast-moving sports, and this type of photography requires a special type of fill-flash. Generally, your flash sync speed (the highest shutter speed you can use with flash) is around 1?250 sec. This varies from camera to camera, but the bottom line is that if I want to shoot at 1?2000 sec.—and use flash in the image—I need to use high-speed sync.
High-speed sync allows your camera to sync the shutter and flash at very high speeds, even up to 1?8000 sec. Speedlights accomplish this by sending out a lightning-fast pulsing burst so there’s always light on the subject no matter how fast the shutter is moving. The compromise is that your flash distance is greatly limited using one flash, plus high-speed sync drains batteries fast. To remedy this, I use flash-bracket systems that hold multiple flashes.