There are various flash modes in our cameras some are more useful than others, and some are surprisingly useful.
- Auto Flash: This is the mode that your camera chooses by default and it basically means that the camera will turn on the flash when it thinks you need it (when there's not enough light)
- Flash Off: This simply turns the flash off (this is the mode I use the most because I often want more natural looking images and the on-camera flash tends to introduce such an artificial looking light quality that it affects the aesthetics of the image.
- Flash On: This is when the flash will go off no matter what; even in bright sunlight. Sometimes it is called fill flash because when you use it in bright sunlight it will help fill in the shadows with light
- Red Eye Reduction: This is when the flash either fires a couple of times before taking the exposure, or a small light comes on just before the exposure and the final flash. The concept here is to try to contract the dialated irises of your portrait subject and thereby eliminate the amount of refelcted light from inside the eyes. Thereby reducing "red-eye".
- Slow Flash: Sometimes this is called night mode and may actually be in a different menu or button on your camera separate from the other flash modes. This is basically when the flash goes off, but doesn't tell the light meter in your camera, so that your light meter sets the camera for the ambient light only. The result is a mixture of flash light and the ambient light in your scene.
Flash Sync Problems
At very fast shutter speeds, you shutter will not allow the flash to provide illumination across the entire sensor. The fastest shutter most cameras are allowed to use with flash is 1/200.
Slow Flash Examples