When bouncing a flash, you may need more flash power than you have available. To ensure you have enough, do the follwoing:
- Use an ISO of at least 400. You may need higher ,especially if ceilings are high or non-reflective.
- Use an aperture of, say, f/5.6 or wider.
- Test your bounce environment by turning the flash to MANUAL mode at full power (1/1, or 100%). Fire. If the picture is overexposed, you have enough power; go back to TTL and start your shoot. If not, then raise ISO and open aperture, or move to a better environment.
Simple steps that can avoid a lot of pain – and TTL flash can do a good job, like here in Anastasia’s picture a few days ago: