Fill Flash can be used when subject is backlit or sidelit to eliminate silhouettes or shadows.
Flash Fact #3
Flash expose is not affected by shutter speed.
Flash Fact #4
Flash illumination is dramatically affected by distance.
Flash Fact #5
Your camera measures ambient light and flash illumination separately.
Flash Fact #6
Without automatic flash metering, the flash illumination is measured after the shutter button is pressed, and the flash output is adjusted accordingly.
Flash Fact #7
Every SLR camera with a mechanical shutter box has a maximum flash sync shutter speed.
Flash Fact #8
Harsh lighting, washed out subjects and red eye can be eliminated by using diffusers and light bouncing
Flash Fact #9
It is possible to change the order of when the flash fires using "Rear curtain Sync"